diff --git a/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/ClientUtils.mustache b/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/ClientUtils.mustache
index 6e7f9809f237..29043e9ca282 100644
--- a/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/ClientUtils.mustache
+++ b/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/ClientUtils.mustache
@@ -407,6 +407,35 @@ using System.Net.Http.Headers;
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/api.mustache b/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/api.mustache
index 0d86d73de3c1..dac3c682f0d3 100644
--- a/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/api.mustache
+++ b/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/api.mustache
@@ -452,23 +452,6 @@ namespace {{packageName}}.{{apiPackage}}
 
                     {{/-last}}
                     {{/queryParams}}
-                    {{#constantParams}}
-                    {{#isHeaderParam}}
-                    // Set client side default value of Header Param "{{baseName}}".
-                    httpRequestMessageLocalVar.Headers.Add("{{baseName}}", ClientUtils.ParameterToString({{#_enum}}"{{{.}}}"{{/_enum}})); // Constant header parameter
-                    {{/isHeaderParam}}
-                    {{/constantParams}}
-                    {{#headerParams}}
-                    {{#required}}
-                    httpRequestMessageLocalVar.Headers.Add("{{baseName}}", ClientUtils.ParameterToString({{paramName}}));
-
-                    {{/required}}
-                    {{^required}}
-                    if ({{paramName}}.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("{{baseName}}", ClientUtils.ParameterToString({{paramName}}.Value));
-
-                    {{/required}}
-                    {{/headerParams}}
                     {{#formParams}}
                     {{#-first}}
                     {{#isMultipart}}
@@ -561,18 +544,65 @@ namespace {{packageName}}.{{apiPackage}}
                     {{/formParams}}
                     {{#bodyParam}}
                     {{#required}}
-                    httpRequestMessageLocalVar.Content = ({{paramName}}{{^required}}.Value{{/required}} as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = ({{paramName}}{{^required}}.Value{{/required}} as object) is {{packageName}}.{{clientPackage}}.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize({{paramName}}{{^required}}.Value{{/required}}, _jsonSerializerOptions));
                     {{/required}}
                     {{^required}}
                     if ({{paramName}}.IsSet)
-                        httpRequestMessageLocalVar.Content = ({{paramName}}{{^required}}.Value{{/required}} as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize({{paramName}}{{^required}}.Value{{/required}}, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = ({{paramName}}{{^required}}.Value{{/required}} as object) is {{packageName}}.{{clientPackage}}.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize({{paramName}}{{^required}}.Value{{/required}}, _jsonSerializerOptions));
+                    }
                     {{/required}}
 
                     {{/bodyParam}}
+
+                    {{#constantParams}}
+                    {{#isHeaderParam}}
+                    // Set client side default value of Header Param "{{baseName}}".                    
+                    if (ClientUtils.IsContentHeader("{{baseName}}"))
+                    {
+                        httpRequestMessageLocalVar.Content.Headers.Add("{{baseName}}", ClientUtils.ParameterToString({{#_enum}}"{{{.}}}"{{/_enum}})); // Constant header parameter
+                    }
+                    else
+                    {
+                        httpRequestMessageLocalVar.Headers.Add("{{baseName}}", ClientUtils.ParameterToString({{#_enum}}"{{{.}}}"{{/_enum}})); // Constant header parameter
+                    }
+
+                    {{/isHeaderParam}}
+                    {{/constantParams}}
+                    {{#headerParams}}
+                    {{#required}}
+                    // Set client side default value of Header Param "{{baseName}}".                    
+                    if (ClientUtils.IsContentHeader("{{baseName}}"))
+                    {
+                        httpRequestMessageLocalVar.Content?.Headers.Add("{{baseName}}", ClientUtils.ParameterToString({{paramName}}));
+                    }
+                    else
+                    {
+                        httpRequestMessageLocalVar.Headers.Add("{{baseName}}", ClientUtils.ParameterToString({{paramName}}));
+                    }
+
+                    {{/required}}
+                    {{^required}}
+                    if ({{paramName}}.IsSet)
+                    {
+                      // Set client side default value of Header Param "{{baseName}}".                    
+                      if (ClientUtils.IsContentHeader("{{baseName}}"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("{{baseName}}", ClientUtils.ParameterToString({{paramName}}.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("{{baseName}}", ClientUtils.ParameterToString({{paramName}}.Value));
+                      }
+                    }
+
+                    {{/required}}
+                    {{/headerParams}}
+
                     {{#authMethods}}
                     {{#-first}}
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
@@ -907,4 +937,4 @@ namespace {{packageName}}.{{apiPackage}}
     }
     {{/operations}}
 }
-{{/lambda.trimLineBreaks}}
+{{/lambda.trimLineBreaks}}
\ No newline at end of file
diff --git a/samples/client/petstore/csharp/generichost/latest/ComposedEnum/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/latest/ComposedEnum/src/Org.OpenAPITools/Client/ClientUtils.cs
index 3c7e3f8809dc..610f4d277860 100644
--- a/samples/client/petstore/csharp/generichost/latest/ComposedEnum/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/latest/ComposedEnum/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -307,6 +307,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/latest/HelloWorld/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/latest/HelloWorld/src/Org.OpenAPITools/Api/DefaultApi.cs
index 08bee9e4dc55..886510d697ba 100644
--- a/samples/client/petstore/csharp/generichost/latest/HelloWorld/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/latest/HelloWorld/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -249,9 +249,11 @@ public async Task<IHelloWorldPostApiResponse> HelloWorldPostAsync(Option<HelloWo
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/helloWorld");
 
                     if (helloWorldPostRequest.IsSet)
-                        httpRequestMessageLocalVar.Content = (helloWorldPostRequest.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(helloWorldPostRequest.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (helloWorldPostRequest.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(helloWorldPostRequest.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
diff --git a/samples/client/petstore/csharp/generichost/latest/HelloWorld/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/latest/HelloWorld/src/Org.OpenAPITools/Client/ClientUtils.cs
index 78e03361249d..b0f1eb910604 100644
--- a/samples/client/petstore/csharp/generichost/latest/HelloWorld/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/latest/HelloWorld/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -301,6 +301,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index 3cd28f988823..e901eccefde7 100644
--- a/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -303,6 +303,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Api/DefaultApi.cs
index 48a14d7ac8e1..6c73040ca3cb 100644
--- a/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -230,9 +230,11 @@ public async Task<IOneOfArrayApiResponse> OneOfArrayAsync(Option<OneOfArrayReque
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/one-of-array");
 
                     if (oneOfArrayRequest.IsSet)
-                        httpRequestMessageLocalVar.Content = (oneOfArrayRequest.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(oneOfArrayRequest.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (oneOfArrayRequest.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(oneOfArrayRequest.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
diff --git a/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Client/ClientUtils.cs
index db80cd11d531..f0707a1ac4c9 100644
--- a/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -301,6 +301,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/latest/Tags/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/latest/Tags/src/Org.OpenAPITools/Client/ClientUtils.cs
index 48719ee3a820..5336e74e8322 100644
--- a/samples/client/petstore/csharp/generichost/latest/Tags/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/latest/Tags/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -327,6 +327,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index e108a9106564..04b8da36fe38 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -277,8 +277,8 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         ? "/another-fake/dummy"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/another-fake/dummy");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Api/FakeApi.cs
index b035dd5c9cd1..237406dab61f 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -1604,9 +1604,11 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/boolean");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -1859,9 +1861,11 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/composite");
 
                     if (outerComposite.IsSet)
-                        httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2101,9 +2105,11 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/number");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2368,9 +2374,11 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -3276,8 +3284,8 @@ public async Task<ITestAdditionalPropertiesReferenceApiResponse> TestAdditionalP
                         ? "/fake/additionalProperties-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/additionalProperties-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3489,8 +3497,8 @@ public async Task<ITestBodyWithFileSchemaApiResponse> TestBodyWithFileSchemaAsyn
                         ? "/fake/body-with-file-schema"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/body-with-file-schema");
 
-                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(fileSchemaTestClass, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3718,8 +3726,8 @@ public async Task<ITestBodyWithQueryParamsApiResponse> TestBodyWithQueryParamsAs
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3931,8 +3939,8 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         ? "/fake"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -4625,12 +4633,6 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    if (enumHeaderString.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
-
-                    if (enumHeaderStringArray.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
-
                     List<KeyValuePair<string, string?>> formParameterLocalVars = new List<KeyValuePair<string, string?>>();
 
                     if (enumFormString.IsSet)
@@ -4642,6 +4644,32 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
                     if (formParameterLocalVars.Count > 0)
                         httpRequestMessageLocalVar.Content = new FormUrlEncodedContent(formParameterLocalVars);
 
+                    if (enumHeaderString.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                    }
+
+                    if (enumHeaderStringArray.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string_array".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string_array"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                    }
+
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
                     string[] contentTypes = new string[] {
@@ -4882,10 +4910,28 @@ public async Task<ITestGroupParametersApiResponse> TestGroupParametersAsync(bool
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    // Set client side default value of Header Param "required_boolean_group".                    
+                    if (ClientUtils.IsContentHeader("required_boolean_group"))
+                    {
+                        httpRequestMessageLocalVar.Content?.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
+                    else
+                    {
+                        httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
 
                     if (booleanGroup.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                    {
+                      // Set client side default value of Header Param "boolean_group".                    
+                      if (ClientUtils.IsContentHeader("boolean_group"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5098,8 +5144,8 @@ public async Task<ITestInlineAdditionalPropertiesApiResponse> TestInlineAddition
                         ? "/fake/inline-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5311,8 +5357,8 @@ public async Task<ITestInlineFreeformAdditionalPropertiesApiResponse> TestInline
                         ? "/fake/inline-freeform-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-freeform-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(testInlineFreeformAdditionalPropertiesRequest, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -6037,8 +6083,8 @@ public async Task<ITestStringMapReferenceApiResponse> TestStringMapReferenceAsyn
                         ? "/fake/stringMap-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/stringMap-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index f3ac29a27b3f..980b7a0c1f89 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -279,8 +279,8 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
 
                     System.Collections.Specialized.NameValueCollection parseQueryStringLocalVar = System.Web.HttpUtility.ParseQueryString(string.Empty);
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Api/PetApi.cs
index c780f8623263..9d06e1ac4a9e 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Api/PetApi.cs
@@ -836,8 +836,8 @@ public async Task<IAddPetApiResponse> AddPetAsync(Pet pet, System.Threading.Canc
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
@@ -1085,7 +1085,17 @@ public async Task<IDeletePetApiResponse> DeletePetAsync(long petId, Option<strin
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7BpetId%7D", Uri.EscapeDataString(petId.ToString()));
 
                     if (apiKey.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                    {
+                      // Set client side default value of Header Param "api_key".                    
+                      if (ClientUtils.IsContentHeader("api_key"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2131,8 +2141,8 @@ public async Task<IUpdatePetApiResponse> UpdatePetAsync(Pet pet, System.Threadin
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Api/StoreApi.cs
index f357fb96d092..08624b36f6ad 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -1140,8 +1140,8 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         ? "/store/order"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/store/order");
 
-                    httpRequestMessageLocalVar.Content = (order as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (order as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(order, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Api/UserApi.cs
index da4e3661c441..c8536386fafb 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Api/UserApi.cs
@@ -714,8 +714,8 @@ public async Task<ICreateUserApiResponse> CreateUserAsync(User user, System.Thre
                         ? "/user"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -927,8 +927,8 @@ public async Task<ICreateUsersWithArrayInputApiResponse> CreateUsersWithArrayInp
                         ? "/user/createWithArray"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithArray");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -1140,8 +1140,8 @@ public async Task<ICreateUsersWithListInputApiResponse> CreateUsersWithListInput
                         ? "/user/createWithList"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithList");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2339,8 +2339,8 @@ public async Task<IUpdateUserApiResponse> UpdateUserAsync(User user, string user
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/{username}");
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7Busername%7D", Uri.EscapeDataString(username.ToString()));
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Client/ClientUtils.cs
index 307e2a2ef3d3..6f17300f7494 100644
--- a/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -402,6 +402,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net10/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net10/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index c75a26cd1562..2157bc68a4f5 100644
--- a/samples/client/petstore/csharp/generichost/net10/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net10/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -316,6 +316,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net10/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net10/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index e3f39f30bec8..64f0a9026639 100644
--- a/samples/client/petstore/csharp/generichost/net10/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net10/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -316,6 +316,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net10/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net10/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
index 0efabe7ad9a2..4da07961deed 100644
--- a/samples/client/petstore/csharp/generichost/net10/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net10/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -301,6 +301,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index 374598ad581f..0de8a13cdbd7 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -275,8 +275,8 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         ? "/another-fake/dummy"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/another-fake/dummy");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
index 8a489ed1f3f3..6638ec4068d1 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -1602,9 +1602,11 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/boolean");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -1857,9 +1859,11 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/composite");
 
                     if (outerComposite.IsSet)
-                        httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2099,9 +2103,11 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/number");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2366,9 +2372,11 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -3274,8 +3282,8 @@ public async Task<ITestAdditionalPropertiesReferenceApiResponse> TestAdditionalP
                         ? "/fake/additionalProperties-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/additionalProperties-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3487,8 +3495,8 @@ public async Task<ITestBodyWithFileSchemaApiResponse> TestBodyWithFileSchemaAsyn
                         ? "/fake/body-with-file-schema"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/body-with-file-schema");
 
-                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(fileSchemaTestClass, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3716,8 +3724,8 @@ public async Task<ITestBodyWithQueryParamsApiResponse> TestBodyWithQueryParamsAs
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3929,8 +3937,8 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         ? "/fake"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -4611,12 +4619,6 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    if (enumHeaderString.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
-
-                    if (enumHeaderStringArray.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
-
                     List<KeyValuePair<string, string>> formParameterLocalVars = new List<KeyValuePair<string, string>>();
 
                     if (enumFormString.IsSet)
@@ -4628,6 +4630,32 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
                     if (formParameterLocalVars.Count > 0)
                         httpRequestMessageLocalVar.Content = new FormUrlEncodedContent(formParameterLocalVars);
 
+                    if (enumHeaderString.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                    }
+
+                    if (enumHeaderStringArray.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string_array".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string_array"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                    }
+
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
                     string[] contentTypes = new string[] {
@@ -4868,10 +4896,28 @@ public async Task<ITestGroupParametersApiResponse> TestGroupParametersAsync(bool
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    // Set client side default value of Header Param "required_boolean_group".                    
+                    if (ClientUtils.IsContentHeader("required_boolean_group"))
+                    {
+                        httpRequestMessageLocalVar.Content?.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
+                    else
+                    {
+                        httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
 
                     if (booleanGroup.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                    {
+                      // Set client side default value of Header Param "boolean_group".                    
+                      if (ClientUtils.IsContentHeader("boolean_group"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5084,8 +5130,8 @@ public async Task<ITestInlineAdditionalPropertiesApiResponse> TestInlineAddition
                         ? "/fake/inline-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5297,8 +5343,8 @@ public async Task<ITestInlineFreeformAdditionalPropertiesApiResponse> TestInline
                         ? "/fake/inline-freeform-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-freeform-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(testInlineFreeformAdditionalPropertiesRequest, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -6023,8 +6069,8 @@ public async Task<ITestStringMapReferenceApiResponse> TestStringMapReferenceAsyn
                         ? "/fake/stringMap-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/stringMap-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index 802d1fdb2ac1..2813dbef14b7 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -277,8 +277,8 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
 
                     System.Collections.Specialized.NameValueCollection parseQueryStringLocalVar = System.Web.HttpUtility.ParseQueryString(string.Empty);
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
index 47c89d10aaa9..7a052a90d955 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
@@ -834,8 +834,8 @@ public async Task<IAddPetApiResponse> AddPetAsync(Pet pet, System.Threading.Canc
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
@@ -1083,7 +1083,17 @@ public async Task<IDeletePetApiResponse> DeletePetAsync(long petId, Option<strin
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7BpetId%7D", Uri.EscapeDataString(petId.ToString()));
 
                     if (apiKey.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                    {
+                      // Set client side default value of Header Param "api_key".                    
+                      if (ClientUtils.IsContentHeader("api_key"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2129,8 +2139,8 @@ public async Task<IUpdatePetApiResponse> UpdatePetAsync(Pet pet, System.Threadin
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
index 036a6d41dfa3..f05331998ad1 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -1138,8 +1138,8 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         ? "/store/order"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/store/order");
 
-                    httpRequestMessageLocalVar.Content = (order as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (order as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(order, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
index c6802990ffc6..ecdf56916766 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
@@ -712,8 +712,8 @@ public async Task<ICreateUserApiResponse> CreateUserAsync(User user, System.Thre
                         ? "/user"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -925,8 +925,8 @@ public async Task<ICreateUsersWithArrayInputApiResponse> CreateUsersWithArrayInp
                         ? "/user/createWithArray"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithArray");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -1138,8 +1138,8 @@ public async Task<ICreateUsersWithListInputApiResponse> CreateUsersWithListInput
                         ? "/user/createWithList"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithList");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2337,8 +2337,8 @@ public async Task<IUpdateUserApiResponse> UpdateUserAsync(User user, string user
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/{username}");
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7Busername%7D", Uri.EscapeDataString(username.ToString()));
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
index 97b8745cc47b..be99808e8e53 100644
--- a/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -411,6 +411,35 @@ public static string GetDiscriminator(Utf8JsonReader utf8JsonReader, string disc
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index e108a9106564..04b8da36fe38 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -277,8 +277,8 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         ? "/another-fake/dummy"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/another-fake/dummy");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeApi.cs
index 7504f8b34bca..9242390191ce 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -1604,9 +1604,11 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/boolean");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -1859,9 +1861,11 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/composite");
 
                     if (outerComposite.IsSet)
-                        httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2101,9 +2105,11 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/number");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2368,9 +2374,11 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -3276,8 +3284,8 @@ public async Task<ITestAdditionalPropertiesReferenceApiResponse> TestAdditionalP
                         ? "/fake/additionalProperties-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/additionalProperties-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3489,8 +3497,8 @@ public async Task<ITestBodyWithFileSchemaApiResponse> TestBodyWithFileSchemaAsyn
                         ? "/fake/body-with-file-schema"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/body-with-file-schema");
 
-                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(fileSchemaTestClass, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3718,8 +3726,8 @@ public async Task<ITestBodyWithQueryParamsApiResponse> TestBodyWithQueryParamsAs
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3931,8 +3939,8 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         ? "/fake"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -4625,12 +4633,6 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    if (enumHeaderString.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
-
-                    if (enumHeaderStringArray.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
-
                     List<KeyValuePair<string, string?>> formParameterLocalVars = new List<KeyValuePair<string, string?>>();
 
                     if (enumFormString.IsSet)
@@ -4642,6 +4644,32 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
                     if (formParameterLocalVars.Count > 0)
                         httpRequestMessageLocalVar.Content = new FormUrlEncodedContent(formParameterLocalVars);
 
+                    if (enumHeaderString.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                    }
+
+                    if (enumHeaderStringArray.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string_array".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string_array"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                    }
+
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
                     string[] contentTypes = new string[] {
@@ -4882,10 +4910,28 @@ public async Task<ITestGroupParametersApiResponse> TestGroupParametersAsync(bool
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    // Set client side default value of Header Param "required_boolean_group".                    
+                    if (ClientUtils.IsContentHeader("required_boolean_group"))
+                    {
+                        httpRequestMessageLocalVar.Content?.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
+                    else
+                    {
+                        httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
 
                     if (booleanGroup.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                    {
+                      // Set client side default value of Header Param "boolean_group".                    
+                      if (ClientUtils.IsContentHeader("boolean_group"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5098,8 +5144,8 @@ public async Task<ITestInlineAdditionalPropertiesApiResponse> TestInlineAddition
                         ? "/fake/inline-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5311,8 +5357,8 @@ public async Task<ITestInlineFreeformAdditionalPropertiesApiResponse> TestInline
                         ? "/fake/inline-freeform-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-freeform-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(testInlineFreeformAdditionalPropertiesRequest, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -6037,8 +6083,8 @@ public async Task<ITestStringMapReferenceApiResponse> TestStringMapReferenceAsyn
                         ? "/fake/stringMap-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/stringMap-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index f3ac29a27b3f..980b7a0c1f89 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -279,8 +279,8 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
 
                     System.Collections.Specialized.NameValueCollection parseQueryStringLocalVar = System.Web.HttpUtility.ParseQueryString(string.Empty);
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Api/PetApi.cs
index c780f8623263..9d06e1ac4a9e 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Api/PetApi.cs
@@ -836,8 +836,8 @@ public async Task<IAddPetApiResponse> AddPetAsync(Pet pet, System.Threading.Canc
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
@@ -1085,7 +1085,17 @@ public async Task<IDeletePetApiResponse> DeletePetAsync(long petId, Option<strin
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7BpetId%7D", Uri.EscapeDataString(petId.ToString()));
 
                     if (apiKey.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                    {
+                      // Set client side default value of Header Param "api_key".                    
+                      if (ClientUtils.IsContentHeader("api_key"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2131,8 +2141,8 @@ public async Task<IUpdatePetApiResponse> UpdatePetAsync(Pet pet, System.Threadin
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Api/StoreApi.cs
index f357fb96d092..08624b36f6ad 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -1140,8 +1140,8 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         ? "/store/order"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/store/order");
 
-                    httpRequestMessageLocalVar.Content = (order as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (order as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(order, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Api/UserApi.cs
index da4e3661c441..c8536386fafb 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Api/UserApi.cs
@@ -714,8 +714,8 @@ public async Task<ICreateUserApiResponse> CreateUserAsync(User user, System.Thre
                         ? "/user"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -927,8 +927,8 @@ public async Task<ICreateUsersWithArrayInputApiResponse> CreateUsersWithArrayInp
                         ? "/user/createWithArray"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithArray");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -1140,8 +1140,8 @@ public async Task<ICreateUsersWithListInputApiResponse> CreateUsersWithListInput
                         ? "/user/createWithList"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithList");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2339,8 +2339,8 @@ public async Task<IUpdateUserApiResponse> UpdateUserAsync(User user, string user
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/{username}");
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7Busername%7D", Uri.EscapeDataString(username.ToString()));
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Client/ClientUtils.cs
index a66181bb5473..f442dd44bfa2 100644
--- a/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net10/NullReferenceTypes/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -417,6 +417,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net10/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net10/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index e3f39f30bec8..64f0a9026639 100644
--- a/samples/client/petstore/csharp/generichost/net10/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net10/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -316,6 +316,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index 374598ad581f..0de8a13cdbd7 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -275,8 +275,8 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         ? "/another-fake/dummy"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/another-fake/dummy");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
index 271fbfea2636..46b99593f1d7 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -1602,9 +1602,11 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/boolean");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -1857,9 +1859,11 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/composite");
 
                     if (outerComposite.IsSet)
-                        httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2099,9 +2103,11 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/number");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2366,9 +2372,11 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -3274,8 +3282,8 @@ public async Task<ITestAdditionalPropertiesReferenceApiResponse> TestAdditionalP
                         ? "/fake/additionalProperties-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/additionalProperties-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3487,8 +3495,8 @@ public async Task<ITestBodyWithFileSchemaApiResponse> TestBodyWithFileSchemaAsyn
                         ? "/fake/body-with-file-schema"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/body-with-file-schema");
 
-                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(fileSchemaTestClass, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3716,8 +3724,8 @@ public async Task<ITestBodyWithQueryParamsApiResponse> TestBodyWithQueryParamsAs
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3929,8 +3937,8 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         ? "/fake"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -4623,12 +4631,6 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    if (enumHeaderString.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
-
-                    if (enumHeaderStringArray.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
-
                     List<KeyValuePair<string, string>> formParameterLocalVars = new List<KeyValuePair<string, string>>();
 
                     if (enumFormString.IsSet)
@@ -4640,6 +4642,32 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
                     if (formParameterLocalVars.Count > 0)
                         httpRequestMessageLocalVar.Content = new FormUrlEncodedContent(formParameterLocalVars);
 
+                    if (enumHeaderString.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                    }
+
+                    if (enumHeaderStringArray.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string_array".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string_array"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                    }
+
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
                     string[] contentTypes = new string[] {
@@ -4880,10 +4908,28 @@ public async Task<ITestGroupParametersApiResponse> TestGroupParametersAsync(bool
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    // Set client side default value of Header Param "required_boolean_group".                    
+                    if (ClientUtils.IsContentHeader("required_boolean_group"))
+                    {
+                        httpRequestMessageLocalVar.Content?.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
+                    else
+                    {
+                        httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
 
                     if (booleanGroup.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                    {
+                      // Set client side default value of Header Param "boolean_group".                    
+                      if (ClientUtils.IsContentHeader("boolean_group"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5096,8 +5142,8 @@ public async Task<ITestInlineAdditionalPropertiesApiResponse> TestInlineAddition
                         ? "/fake/inline-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5309,8 +5355,8 @@ public async Task<ITestInlineFreeformAdditionalPropertiesApiResponse> TestInline
                         ? "/fake/inline-freeform-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-freeform-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(testInlineFreeformAdditionalPropertiesRequest, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -6035,8 +6081,8 @@ public async Task<ITestStringMapReferenceApiResponse> TestStringMapReferenceAsyn
                         ? "/fake/stringMap-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/stringMap-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index 802d1fdb2ac1..2813dbef14b7 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -277,8 +277,8 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
 
                     System.Collections.Specialized.NameValueCollection parseQueryStringLocalVar = System.Web.HttpUtility.ParseQueryString(string.Empty);
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
index af5a07843603..0843443b2ae3 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
@@ -834,8 +834,8 @@ public async Task<IAddPetApiResponse> AddPetAsync(Pet pet, System.Threading.Canc
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
@@ -1083,7 +1083,17 @@ public async Task<IDeletePetApiResponse> DeletePetAsync(long petId, Option<strin
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7BpetId%7D", Uri.EscapeDataString(petId.ToString()));
 
                     if (apiKey.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                    {
+                      // Set client side default value of Header Param "api_key".                    
+                      if (ClientUtils.IsContentHeader("api_key"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2129,8 +2139,8 @@ public async Task<IUpdatePetApiResponse> UpdatePetAsync(Pet pet, System.Threadin
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
index 036a6d41dfa3..f05331998ad1 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -1138,8 +1138,8 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         ? "/store/order"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/store/order");
 
-                    httpRequestMessageLocalVar.Content = (order as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (order as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(order, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
index c6802990ffc6..ecdf56916766 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
@@ -712,8 +712,8 @@ public async Task<ICreateUserApiResponse> CreateUserAsync(User user, System.Thre
                         ? "/user"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -925,8 +925,8 @@ public async Task<ICreateUsersWithArrayInputApiResponse> CreateUsersWithArrayInp
                         ? "/user/createWithArray"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithArray");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -1138,8 +1138,8 @@ public async Task<ICreateUsersWithListInputApiResponse> CreateUsersWithListInput
                         ? "/user/createWithList"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithList");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2337,8 +2337,8 @@ public async Task<IUpdateUserApiResponse> UpdateUserAsync(User user, string user
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/{username}");
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7Busername%7D", Uri.EscapeDataString(username.ToString()));
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
index 3dfb7ecffbed..9ea7d8118c3b 100644
--- a/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net10/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -415,6 +415,35 @@ public static string GetDiscriminator(Utf8JsonReader utf8JsonReader, string disc
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index e108a9106564..04b8da36fe38 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -277,8 +277,8 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         ? "/another-fake/dummy"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/another-fake/dummy");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Api/FakeApi.cs
index 7504f8b34bca..9242390191ce 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -1604,9 +1604,11 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/boolean");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -1859,9 +1861,11 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/composite");
 
                     if (outerComposite.IsSet)
-                        httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2101,9 +2105,11 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/number");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2368,9 +2374,11 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -3276,8 +3284,8 @@ public async Task<ITestAdditionalPropertiesReferenceApiResponse> TestAdditionalP
                         ? "/fake/additionalProperties-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/additionalProperties-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3489,8 +3497,8 @@ public async Task<ITestBodyWithFileSchemaApiResponse> TestBodyWithFileSchemaAsyn
                         ? "/fake/body-with-file-schema"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/body-with-file-schema");
 
-                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(fileSchemaTestClass, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3718,8 +3726,8 @@ public async Task<ITestBodyWithQueryParamsApiResponse> TestBodyWithQueryParamsAs
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3931,8 +3939,8 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         ? "/fake"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -4625,12 +4633,6 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    if (enumHeaderString.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
-
-                    if (enumHeaderStringArray.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
-
                     List<KeyValuePair<string, string?>> formParameterLocalVars = new List<KeyValuePair<string, string?>>();
 
                     if (enumFormString.IsSet)
@@ -4642,6 +4644,32 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
                     if (formParameterLocalVars.Count > 0)
                         httpRequestMessageLocalVar.Content = new FormUrlEncodedContent(formParameterLocalVars);
 
+                    if (enumHeaderString.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                    }
+
+                    if (enumHeaderStringArray.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string_array".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string_array"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                    }
+
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
                     string[] contentTypes = new string[] {
@@ -4882,10 +4910,28 @@ public async Task<ITestGroupParametersApiResponse> TestGroupParametersAsync(bool
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    // Set client side default value of Header Param "required_boolean_group".                    
+                    if (ClientUtils.IsContentHeader("required_boolean_group"))
+                    {
+                        httpRequestMessageLocalVar.Content?.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
+                    else
+                    {
+                        httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
 
                     if (booleanGroup.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                    {
+                      // Set client side default value of Header Param "boolean_group".                    
+                      if (ClientUtils.IsContentHeader("boolean_group"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5098,8 +5144,8 @@ public async Task<ITestInlineAdditionalPropertiesApiResponse> TestInlineAddition
                         ? "/fake/inline-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5311,8 +5357,8 @@ public async Task<ITestInlineFreeformAdditionalPropertiesApiResponse> TestInline
                         ? "/fake/inline-freeform-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-freeform-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(testInlineFreeformAdditionalPropertiesRequest, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -6037,8 +6083,8 @@ public async Task<ITestStringMapReferenceApiResponse> TestStringMapReferenceAsyn
                         ? "/fake/stringMap-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/stringMap-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index f3ac29a27b3f..980b7a0c1f89 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -279,8 +279,8 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
 
                     System.Collections.Specialized.NameValueCollection parseQueryStringLocalVar = System.Web.HttpUtility.ParseQueryString(string.Empty);
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Api/PetApi.cs
index c780f8623263..9d06e1ac4a9e 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Api/PetApi.cs
@@ -836,8 +836,8 @@ public async Task<IAddPetApiResponse> AddPetAsync(Pet pet, System.Threading.Canc
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
@@ -1085,7 +1085,17 @@ public async Task<IDeletePetApiResponse> DeletePetAsync(long petId, Option<strin
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7BpetId%7D", Uri.EscapeDataString(petId.ToString()));
 
                     if (apiKey.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                    {
+                      // Set client side default value of Header Param "api_key".                    
+                      if (ClientUtils.IsContentHeader("api_key"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2131,8 +2141,8 @@ public async Task<IUpdatePetApiResponse> UpdatePetAsync(Pet pet, System.Threadin
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Api/StoreApi.cs
index f357fb96d092..08624b36f6ad 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -1140,8 +1140,8 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         ? "/store/order"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/store/order");
 
-                    httpRequestMessageLocalVar.Content = (order as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (order as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(order, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Api/UserApi.cs
index da4e3661c441..c8536386fafb 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Api/UserApi.cs
@@ -714,8 +714,8 @@ public async Task<ICreateUserApiResponse> CreateUserAsync(User user, System.Thre
                         ? "/user"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -927,8 +927,8 @@ public async Task<ICreateUsersWithArrayInputApiResponse> CreateUsersWithArrayInp
                         ? "/user/createWithArray"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithArray");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -1140,8 +1140,8 @@ public async Task<ICreateUsersWithListInputApiResponse> CreateUsersWithListInput
                         ? "/user/createWithList"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithList");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2339,8 +2339,8 @@ public async Task<IUpdateUserApiResponse> UpdateUserAsync(User user, string user
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/{username}");
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7Busername%7D", Uri.EscapeDataString(username.ToString()));
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Client/ClientUtils.cs
index a66181bb5473..f442dd44bfa2 100644
--- a/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net10/SourceGeneration/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -417,6 +417,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net10/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net10/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
index 55d79ce4b6a8..3310db6b99d8 100644
--- a/samples/client/petstore/csharp/generichost/net10/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net10/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -301,6 +301,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.7/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.7/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index edb65b8265db..a8017239f2d0 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -311,6 +311,35 @@ public static string GetDiscriminator(Utf8JsonReader utf8JsonReader, string disc
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index 69f7ad2b7116..64f174fb00d2 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -311,6 +311,35 @@ public static string GetDiscriminator(Utf8JsonReader utf8JsonReader, string disc
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
index 217a64d7d771..06a270135661 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -296,6 +296,35 @@ public static string GetDiscriminator(Utf8JsonReader utf8JsonReader, string disc
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index 7eeebe9c25d2..1540faaeb1cf 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -275,8 +275,8 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         ? "/another-fake/dummy"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/another-fake/dummy");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
index 98684187061c..e978aa8b5292 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -1601,9 +1601,11 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/boolean");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -1855,9 +1857,11 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/composite");
 
                     if (outerComposite.IsSet)
-                        httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2096,9 +2100,11 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/number");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2362,9 +2368,11 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -3266,8 +3274,8 @@ public async Task<ITestAdditionalPropertiesReferenceApiResponse> TestAdditionalP
                         ? "/fake/additionalProperties-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/additionalProperties-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3479,8 +3487,8 @@ public async Task<ITestBodyWithFileSchemaApiResponse> TestBodyWithFileSchemaAsyn
                         ? "/fake/body-with-file-schema"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/body-with-file-schema");
 
-                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(fileSchemaTestClass, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3708,8 +3716,8 @@ public async Task<ITestBodyWithQueryParamsApiResponse> TestBodyWithQueryParamsAs
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3921,8 +3929,8 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         ? "/fake"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -4602,12 +4610,6 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    if (enumHeaderString.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
-
-                    if (enumHeaderStringArray.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
-
                     List<KeyValuePair<string, string>> formParameterLocalVars = new List<KeyValuePair<string, string>>();
 
                     if (enumFormString.IsSet)
@@ -4619,6 +4621,32 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
                     if (formParameterLocalVars.Count > 0)
                         httpRequestMessageLocalVar.Content = new FormUrlEncodedContent(formParameterLocalVars);
 
+                    if (enumHeaderString.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                    }
+
+                    if (enumHeaderStringArray.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string_array".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string_array"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                    }
+
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
                     string[] contentTypes = new string[] {
@@ -4859,10 +4887,28 @@ public async Task<ITestGroupParametersApiResponse> TestGroupParametersAsync(bool
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    // Set client side default value of Header Param "required_boolean_group".                    
+                    if (ClientUtils.IsContentHeader("required_boolean_group"))
+                    {
+                        httpRequestMessageLocalVar.Content?.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
+                    else
+                    {
+                        httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
 
                     if (booleanGroup.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                    {
+                      // Set client side default value of Header Param "boolean_group".                    
+                      if (ClientUtils.IsContentHeader("boolean_group"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5074,8 +5120,8 @@ public async Task<ITestInlineAdditionalPropertiesApiResponse> TestInlineAddition
                         ? "/fake/inline-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5287,8 +5333,8 @@ public async Task<ITestInlineFreeformAdditionalPropertiesApiResponse> TestInline
                         ? "/fake/inline-freeform-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-freeform-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(testInlineFreeformAdditionalPropertiesRequest, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -6012,8 +6058,8 @@ public async Task<ITestStringMapReferenceApiResponse> TestStringMapReferenceAsyn
                         ? "/fake/stringMap-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/stringMap-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index da2c72009ed0..0fe14400f4d6 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -277,8 +277,8 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
 
                     System.Collections.Specialized.NameValueCollection parseQueryStringLocalVar = System.Web.HttpUtility.ParseQueryString(string.Empty);
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
index 4f546bd46274..a7310cdc0f0a 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
@@ -834,8 +834,8 @@ public async Task<IAddPetApiResponse> AddPetAsync(Pet pet, System.Threading.Canc
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
@@ -1083,7 +1083,17 @@ public async Task<IDeletePetApiResponse> DeletePetAsync(long petId, Option<strin
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7BpetId%7D", Uri.EscapeDataString(petId.ToString()));
 
                     if (apiKey.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                    {
+                      // Set client side default value of Header Param "api_key".                    
+                      if (ClientUtils.IsContentHeader("api_key"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2125,8 +2135,8 @@ public async Task<IUpdatePetApiResponse> UpdatePetAsync(Pet pet, System.Threadin
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
index c73432cbeadc..9c7430992dbb 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -1135,8 +1135,8 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         ? "/store/order"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/store/order");
 
-                    httpRequestMessageLocalVar.Content = (order as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (order as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(order, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
index 22514301a2c9..4c61cc91448a 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
@@ -704,8 +704,8 @@ public async Task<ICreateUserApiResponse> CreateUserAsync(User user, System.Thre
                         ? "/user"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -917,8 +917,8 @@ public async Task<ICreateUsersWithArrayInputApiResponse> CreateUsersWithArrayInp
                         ? "/user/createWithArray"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithArray");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -1130,8 +1130,8 @@ public async Task<ICreateUsersWithListInputApiResponse> CreateUsersWithListInput
                         ? "/user/createWithList"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithList");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2298,8 +2298,8 @@ public async Task<IUpdateUserApiResponse> UpdateUserAsync(User user, string user
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/{username}");
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7Busername%7D", Uri.EscapeDataString(username.ToString()));
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
index 585f78b2c231..965dcceeeeb5 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -411,6 +411,35 @@ public static string GetDiscriminator(Utf8JsonReader utf8JsonReader, string disc
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index 69f7ad2b7116..64f174fb00d2 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -311,6 +311,35 @@ public static string GetDiscriminator(Utf8JsonReader utf8JsonReader, string disc
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index 7eeebe9c25d2..1540faaeb1cf 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -275,8 +275,8 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         ? "/another-fake/dummy"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/another-fake/dummy");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
index 700574a85fba..8f61b4a3e376 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -1601,9 +1601,11 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/boolean");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -1855,9 +1857,11 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/composite");
 
                     if (outerComposite.IsSet)
-                        httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2096,9 +2100,11 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/number");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2362,9 +2368,11 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -3266,8 +3274,8 @@ public async Task<ITestAdditionalPropertiesReferenceApiResponse> TestAdditionalP
                         ? "/fake/additionalProperties-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/additionalProperties-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3479,8 +3487,8 @@ public async Task<ITestBodyWithFileSchemaApiResponse> TestBodyWithFileSchemaAsyn
                         ? "/fake/body-with-file-schema"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/body-with-file-schema");
 
-                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(fileSchemaTestClass, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3708,8 +3716,8 @@ public async Task<ITestBodyWithQueryParamsApiResponse> TestBodyWithQueryParamsAs
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3921,8 +3929,8 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         ? "/fake"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -4614,12 +4622,6 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    if (enumHeaderString.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
-
-                    if (enumHeaderStringArray.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
-
                     List<KeyValuePair<string, string>> formParameterLocalVars = new List<KeyValuePair<string, string>>();
 
                     if (enumFormString.IsSet)
@@ -4631,6 +4633,32 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
                     if (formParameterLocalVars.Count > 0)
                         httpRequestMessageLocalVar.Content = new FormUrlEncodedContent(formParameterLocalVars);
 
+                    if (enumHeaderString.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                    }
+
+                    if (enumHeaderStringArray.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string_array".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string_array"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                    }
+
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
                     string[] contentTypes = new string[] {
@@ -4871,10 +4899,28 @@ public async Task<ITestGroupParametersApiResponse> TestGroupParametersAsync(bool
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    // Set client side default value of Header Param "required_boolean_group".                    
+                    if (ClientUtils.IsContentHeader("required_boolean_group"))
+                    {
+                        httpRequestMessageLocalVar.Content?.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
+                    else
+                    {
+                        httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
 
                     if (booleanGroup.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                    {
+                      // Set client side default value of Header Param "boolean_group".                    
+                      if (ClientUtils.IsContentHeader("boolean_group"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5086,8 +5132,8 @@ public async Task<ITestInlineAdditionalPropertiesApiResponse> TestInlineAddition
                         ? "/fake/inline-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5299,8 +5345,8 @@ public async Task<ITestInlineFreeformAdditionalPropertiesApiResponse> TestInline
                         ? "/fake/inline-freeform-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-freeform-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(testInlineFreeformAdditionalPropertiesRequest, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -6024,8 +6070,8 @@ public async Task<ITestStringMapReferenceApiResponse> TestStringMapReferenceAsyn
                         ? "/fake/stringMap-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/stringMap-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index da2c72009ed0..0fe14400f4d6 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -277,8 +277,8 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
 
                     System.Collections.Specialized.NameValueCollection parseQueryStringLocalVar = System.Web.HttpUtility.ParseQueryString(string.Empty);
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
index de209e1450ec..d955b80e8761 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
@@ -834,8 +834,8 @@ public async Task<IAddPetApiResponse> AddPetAsync(Pet pet, System.Threading.Canc
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
@@ -1083,7 +1083,17 @@ public async Task<IDeletePetApiResponse> DeletePetAsync(long petId, Option<strin
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7BpetId%7D", Uri.EscapeDataString(petId.ToString()));
 
                     if (apiKey.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                    {
+                      // Set client side default value of Header Param "api_key".                    
+                      if (ClientUtils.IsContentHeader("api_key"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2125,8 +2135,8 @@ public async Task<IUpdatePetApiResponse> UpdatePetAsync(Pet pet, System.Threadin
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
index c73432cbeadc..9c7430992dbb 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -1135,8 +1135,8 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         ? "/store/order"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/store/order");
 
-                    httpRequestMessageLocalVar.Content = (order as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (order as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(order, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
index 22514301a2c9..4c61cc91448a 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
@@ -704,8 +704,8 @@ public async Task<ICreateUserApiResponse> CreateUserAsync(User user, System.Thre
                         ? "/user"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -917,8 +917,8 @@ public async Task<ICreateUsersWithArrayInputApiResponse> CreateUsersWithArrayInp
                         ? "/user/createWithArray"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithArray");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -1130,8 +1130,8 @@ public async Task<ICreateUsersWithListInputApiResponse> CreateUsersWithListInput
                         ? "/user/createWithList"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithList");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2298,8 +2298,8 @@ public async Task<IUpdateUserApiResponse> UpdateUserAsync(User user, string user
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/{username}");
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7Busername%7D", Uri.EscapeDataString(username.ToString()));
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
index c2d90fee7b00..92d95ba94060 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -415,6 +415,35 @@ public static string GetDiscriminator(Utf8JsonReader utf8JsonReader, string disc
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.7/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.7/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
index f421f6d6c00b..196d6f474252 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -296,6 +296,35 @@ public static string GetDiscriminator(Utf8JsonReader utf8JsonReader, string disc
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.8/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.8/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index edb65b8265db..a8017239f2d0 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -311,6 +311,35 @@ public static string GetDiscriminator(Utf8JsonReader utf8JsonReader, string disc
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index 69f7ad2b7116..64f174fb00d2 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -311,6 +311,35 @@ public static string GetDiscriminator(Utf8JsonReader utf8JsonReader, string disc
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
index 217a64d7d771..06a270135661 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -296,6 +296,35 @@ public static string GetDiscriminator(Utf8JsonReader utf8JsonReader, string disc
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index 7eeebe9c25d2..1540faaeb1cf 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -275,8 +275,8 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         ? "/another-fake/dummy"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/another-fake/dummy");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
index 98684187061c..e978aa8b5292 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -1601,9 +1601,11 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/boolean");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -1855,9 +1857,11 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/composite");
 
                     if (outerComposite.IsSet)
-                        httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2096,9 +2100,11 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/number");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2362,9 +2368,11 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -3266,8 +3274,8 @@ public async Task<ITestAdditionalPropertiesReferenceApiResponse> TestAdditionalP
                         ? "/fake/additionalProperties-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/additionalProperties-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3479,8 +3487,8 @@ public async Task<ITestBodyWithFileSchemaApiResponse> TestBodyWithFileSchemaAsyn
                         ? "/fake/body-with-file-schema"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/body-with-file-schema");
 
-                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(fileSchemaTestClass, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3708,8 +3716,8 @@ public async Task<ITestBodyWithQueryParamsApiResponse> TestBodyWithQueryParamsAs
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3921,8 +3929,8 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         ? "/fake"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -4602,12 +4610,6 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    if (enumHeaderString.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
-
-                    if (enumHeaderStringArray.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
-
                     List<KeyValuePair<string, string>> formParameterLocalVars = new List<KeyValuePair<string, string>>();
 
                     if (enumFormString.IsSet)
@@ -4619,6 +4621,32 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
                     if (formParameterLocalVars.Count > 0)
                         httpRequestMessageLocalVar.Content = new FormUrlEncodedContent(formParameterLocalVars);
 
+                    if (enumHeaderString.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                    }
+
+                    if (enumHeaderStringArray.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string_array".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string_array"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                    }
+
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
                     string[] contentTypes = new string[] {
@@ -4859,10 +4887,28 @@ public async Task<ITestGroupParametersApiResponse> TestGroupParametersAsync(bool
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    // Set client side default value of Header Param "required_boolean_group".                    
+                    if (ClientUtils.IsContentHeader("required_boolean_group"))
+                    {
+                        httpRequestMessageLocalVar.Content?.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
+                    else
+                    {
+                        httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
 
                     if (booleanGroup.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                    {
+                      // Set client side default value of Header Param "boolean_group".                    
+                      if (ClientUtils.IsContentHeader("boolean_group"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5074,8 +5120,8 @@ public async Task<ITestInlineAdditionalPropertiesApiResponse> TestInlineAddition
                         ? "/fake/inline-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5287,8 +5333,8 @@ public async Task<ITestInlineFreeformAdditionalPropertiesApiResponse> TestInline
                         ? "/fake/inline-freeform-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-freeform-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(testInlineFreeformAdditionalPropertiesRequest, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -6012,8 +6058,8 @@ public async Task<ITestStringMapReferenceApiResponse> TestStringMapReferenceAsyn
                         ? "/fake/stringMap-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/stringMap-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index da2c72009ed0..0fe14400f4d6 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -277,8 +277,8 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
 
                     System.Collections.Specialized.NameValueCollection parseQueryStringLocalVar = System.Web.HttpUtility.ParseQueryString(string.Empty);
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
index 4f546bd46274..a7310cdc0f0a 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
@@ -834,8 +834,8 @@ public async Task<IAddPetApiResponse> AddPetAsync(Pet pet, System.Threading.Canc
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
@@ -1083,7 +1083,17 @@ public async Task<IDeletePetApiResponse> DeletePetAsync(long petId, Option<strin
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7BpetId%7D", Uri.EscapeDataString(petId.ToString()));
 
                     if (apiKey.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                    {
+                      // Set client side default value of Header Param "api_key".                    
+                      if (ClientUtils.IsContentHeader("api_key"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2125,8 +2135,8 @@ public async Task<IUpdatePetApiResponse> UpdatePetAsync(Pet pet, System.Threadin
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
index c73432cbeadc..9c7430992dbb 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -1135,8 +1135,8 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         ? "/store/order"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/store/order");
 
-                    httpRequestMessageLocalVar.Content = (order as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (order as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(order, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
index 22514301a2c9..4c61cc91448a 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
@@ -704,8 +704,8 @@ public async Task<ICreateUserApiResponse> CreateUserAsync(User user, System.Thre
                         ? "/user"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -917,8 +917,8 @@ public async Task<ICreateUsersWithArrayInputApiResponse> CreateUsersWithArrayInp
                         ? "/user/createWithArray"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithArray");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -1130,8 +1130,8 @@ public async Task<ICreateUsersWithListInputApiResponse> CreateUsersWithListInput
                         ? "/user/createWithList"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithList");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2298,8 +2298,8 @@ public async Task<IUpdateUserApiResponse> UpdateUserAsync(User user, string user
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/{username}");
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7Busername%7D", Uri.EscapeDataString(username.ToString()));
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
index 585f78b2c231..965dcceeeeb5 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -411,6 +411,35 @@ public static string GetDiscriminator(Utf8JsonReader utf8JsonReader, string disc
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index 69f7ad2b7116..64f174fb00d2 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -311,6 +311,35 @@ public static string GetDiscriminator(Utf8JsonReader utf8JsonReader, string disc
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index 7eeebe9c25d2..1540faaeb1cf 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -275,8 +275,8 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         ? "/another-fake/dummy"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/another-fake/dummy");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
index 700574a85fba..8f61b4a3e376 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -1601,9 +1601,11 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/boolean");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -1855,9 +1857,11 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/composite");
 
                     if (outerComposite.IsSet)
-                        httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2096,9 +2100,11 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/number");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2362,9 +2368,11 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -3266,8 +3274,8 @@ public async Task<ITestAdditionalPropertiesReferenceApiResponse> TestAdditionalP
                         ? "/fake/additionalProperties-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/additionalProperties-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3479,8 +3487,8 @@ public async Task<ITestBodyWithFileSchemaApiResponse> TestBodyWithFileSchemaAsyn
                         ? "/fake/body-with-file-schema"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/body-with-file-schema");
 
-                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(fileSchemaTestClass, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3708,8 +3716,8 @@ public async Task<ITestBodyWithQueryParamsApiResponse> TestBodyWithQueryParamsAs
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3921,8 +3929,8 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         ? "/fake"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -4614,12 +4622,6 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    if (enumHeaderString.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
-
-                    if (enumHeaderStringArray.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
-
                     List<KeyValuePair<string, string>> formParameterLocalVars = new List<KeyValuePair<string, string>>();
 
                     if (enumFormString.IsSet)
@@ -4631,6 +4633,32 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
                     if (formParameterLocalVars.Count > 0)
                         httpRequestMessageLocalVar.Content = new FormUrlEncodedContent(formParameterLocalVars);
 
+                    if (enumHeaderString.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                    }
+
+                    if (enumHeaderStringArray.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string_array".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string_array"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                    }
+
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
                     string[] contentTypes = new string[] {
@@ -4871,10 +4899,28 @@ public async Task<ITestGroupParametersApiResponse> TestGroupParametersAsync(bool
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    // Set client side default value of Header Param "required_boolean_group".                    
+                    if (ClientUtils.IsContentHeader("required_boolean_group"))
+                    {
+                        httpRequestMessageLocalVar.Content?.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
+                    else
+                    {
+                        httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
 
                     if (booleanGroup.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                    {
+                      // Set client side default value of Header Param "boolean_group".                    
+                      if (ClientUtils.IsContentHeader("boolean_group"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5086,8 +5132,8 @@ public async Task<ITestInlineAdditionalPropertiesApiResponse> TestInlineAddition
                         ? "/fake/inline-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5299,8 +5345,8 @@ public async Task<ITestInlineFreeformAdditionalPropertiesApiResponse> TestInline
                         ? "/fake/inline-freeform-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-freeform-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(testInlineFreeformAdditionalPropertiesRequest, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -6024,8 +6070,8 @@ public async Task<ITestStringMapReferenceApiResponse> TestStringMapReferenceAsyn
                         ? "/fake/stringMap-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/stringMap-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index da2c72009ed0..0fe14400f4d6 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -277,8 +277,8 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
 
                     System.Collections.Specialized.NameValueCollection parseQueryStringLocalVar = System.Web.HttpUtility.ParseQueryString(string.Empty);
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
index de209e1450ec..d955b80e8761 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
@@ -834,8 +834,8 @@ public async Task<IAddPetApiResponse> AddPetAsync(Pet pet, System.Threading.Canc
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
@@ -1083,7 +1083,17 @@ public async Task<IDeletePetApiResponse> DeletePetAsync(long petId, Option<strin
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7BpetId%7D", Uri.EscapeDataString(petId.ToString()));
 
                     if (apiKey.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                    {
+                      // Set client side default value of Header Param "api_key".                    
+                      if (ClientUtils.IsContentHeader("api_key"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2125,8 +2135,8 @@ public async Task<IUpdatePetApiResponse> UpdatePetAsync(Pet pet, System.Threadin
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
index c73432cbeadc..9c7430992dbb 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -1135,8 +1135,8 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         ? "/store/order"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/store/order");
 
-                    httpRequestMessageLocalVar.Content = (order as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (order as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(order, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
index 22514301a2c9..4c61cc91448a 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
@@ -704,8 +704,8 @@ public async Task<ICreateUserApiResponse> CreateUserAsync(User user, System.Thre
                         ? "/user"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -917,8 +917,8 @@ public async Task<ICreateUsersWithArrayInputApiResponse> CreateUsersWithArrayInp
                         ? "/user/createWithArray"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithArray");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -1130,8 +1130,8 @@ public async Task<ICreateUsersWithListInputApiResponse> CreateUsersWithListInput
                         ? "/user/createWithList"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithList");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2298,8 +2298,8 @@ public async Task<IUpdateUserApiResponse> UpdateUserAsync(User user, string user
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/{username}");
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7Busername%7D", Uri.EscapeDataString(username.ToString()));
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
index c2d90fee7b00..92d95ba94060 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -415,6 +415,35 @@ public static string GetDiscriminator(Utf8JsonReader utf8JsonReader, string disc
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
index f421f6d6c00b..196d6f474252 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -296,6 +296,35 @@ public static string GetDiscriminator(Utf8JsonReader utf8JsonReader, string disc
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net8/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net8/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index c75a26cd1562..2157bc68a4f5 100644
--- a/samples/client/petstore/csharp/generichost/net8/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net8/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -316,6 +316,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index e3f39f30bec8..64f0a9026639 100644
--- a/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -316,6 +316,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
index 0efabe7ad9a2..4da07961deed 100644
--- a/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -301,6 +301,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index 374598ad581f..0de8a13cdbd7 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -275,8 +275,8 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         ? "/another-fake/dummy"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/another-fake/dummy");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
index 8a489ed1f3f3..6638ec4068d1 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -1602,9 +1602,11 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/boolean");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -1857,9 +1859,11 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/composite");
 
                     if (outerComposite.IsSet)
-                        httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2099,9 +2103,11 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/number");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2366,9 +2372,11 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -3274,8 +3282,8 @@ public async Task<ITestAdditionalPropertiesReferenceApiResponse> TestAdditionalP
                         ? "/fake/additionalProperties-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/additionalProperties-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3487,8 +3495,8 @@ public async Task<ITestBodyWithFileSchemaApiResponse> TestBodyWithFileSchemaAsyn
                         ? "/fake/body-with-file-schema"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/body-with-file-schema");
 
-                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(fileSchemaTestClass, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3716,8 +3724,8 @@ public async Task<ITestBodyWithQueryParamsApiResponse> TestBodyWithQueryParamsAs
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3929,8 +3937,8 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         ? "/fake"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -4611,12 +4619,6 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    if (enumHeaderString.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
-
-                    if (enumHeaderStringArray.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
-
                     List<KeyValuePair<string, string>> formParameterLocalVars = new List<KeyValuePair<string, string>>();
 
                     if (enumFormString.IsSet)
@@ -4628,6 +4630,32 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
                     if (formParameterLocalVars.Count > 0)
                         httpRequestMessageLocalVar.Content = new FormUrlEncodedContent(formParameterLocalVars);
 
+                    if (enumHeaderString.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                    }
+
+                    if (enumHeaderStringArray.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string_array".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string_array"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                    }
+
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
                     string[] contentTypes = new string[] {
@@ -4868,10 +4896,28 @@ public async Task<ITestGroupParametersApiResponse> TestGroupParametersAsync(bool
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    // Set client side default value of Header Param "required_boolean_group".                    
+                    if (ClientUtils.IsContentHeader("required_boolean_group"))
+                    {
+                        httpRequestMessageLocalVar.Content?.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
+                    else
+                    {
+                        httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
 
                     if (booleanGroup.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                    {
+                      // Set client side default value of Header Param "boolean_group".                    
+                      if (ClientUtils.IsContentHeader("boolean_group"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5084,8 +5130,8 @@ public async Task<ITestInlineAdditionalPropertiesApiResponse> TestInlineAddition
                         ? "/fake/inline-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5297,8 +5343,8 @@ public async Task<ITestInlineFreeformAdditionalPropertiesApiResponse> TestInline
                         ? "/fake/inline-freeform-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-freeform-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(testInlineFreeformAdditionalPropertiesRequest, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -6023,8 +6069,8 @@ public async Task<ITestStringMapReferenceApiResponse> TestStringMapReferenceAsyn
                         ? "/fake/stringMap-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/stringMap-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index 802d1fdb2ac1..2813dbef14b7 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -277,8 +277,8 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
 
                     System.Collections.Specialized.NameValueCollection parseQueryStringLocalVar = System.Web.HttpUtility.ParseQueryString(string.Empty);
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
index 47c89d10aaa9..7a052a90d955 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
@@ -834,8 +834,8 @@ public async Task<IAddPetApiResponse> AddPetAsync(Pet pet, System.Threading.Canc
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
@@ -1083,7 +1083,17 @@ public async Task<IDeletePetApiResponse> DeletePetAsync(long petId, Option<strin
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7BpetId%7D", Uri.EscapeDataString(petId.ToString()));
 
                     if (apiKey.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                    {
+                      // Set client side default value of Header Param "api_key".                    
+                      if (ClientUtils.IsContentHeader("api_key"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2129,8 +2139,8 @@ public async Task<IUpdatePetApiResponse> UpdatePetAsync(Pet pet, System.Threadin
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
index 036a6d41dfa3..f05331998ad1 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -1138,8 +1138,8 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         ? "/store/order"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/store/order");
 
-                    httpRequestMessageLocalVar.Content = (order as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (order as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(order, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
index c6802990ffc6..ecdf56916766 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
@@ -712,8 +712,8 @@ public async Task<ICreateUserApiResponse> CreateUserAsync(User user, System.Thre
                         ? "/user"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -925,8 +925,8 @@ public async Task<ICreateUsersWithArrayInputApiResponse> CreateUsersWithArrayInp
                         ? "/user/createWithArray"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithArray");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -1138,8 +1138,8 @@ public async Task<ICreateUsersWithListInputApiResponse> CreateUsersWithListInput
                         ? "/user/createWithList"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithList");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2337,8 +2337,8 @@ public async Task<IUpdateUserApiResponse> UpdateUserAsync(User user, string user
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/{username}");
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7Busername%7D", Uri.EscapeDataString(username.ToString()));
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
index 97b8745cc47b..be99808e8e53 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -411,6 +411,35 @@ public static string GetDiscriminator(Utf8JsonReader utf8JsonReader, string disc
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index e108a9106564..04b8da36fe38 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -277,8 +277,8 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         ? "/another-fake/dummy"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/another-fake/dummy");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeApi.cs
index 7504f8b34bca..9242390191ce 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -1604,9 +1604,11 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/boolean");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -1859,9 +1861,11 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/composite");
 
                     if (outerComposite.IsSet)
-                        httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2101,9 +2105,11 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/number");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2368,9 +2374,11 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -3276,8 +3284,8 @@ public async Task<ITestAdditionalPropertiesReferenceApiResponse> TestAdditionalP
                         ? "/fake/additionalProperties-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/additionalProperties-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3489,8 +3497,8 @@ public async Task<ITestBodyWithFileSchemaApiResponse> TestBodyWithFileSchemaAsyn
                         ? "/fake/body-with-file-schema"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/body-with-file-schema");
 
-                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(fileSchemaTestClass, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3718,8 +3726,8 @@ public async Task<ITestBodyWithQueryParamsApiResponse> TestBodyWithQueryParamsAs
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3931,8 +3939,8 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         ? "/fake"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -4625,12 +4633,6 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    if (enumHeaderString.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
-
-                    if (enumHeaderStringArray.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
-
                     List<KeyValuePair<string, string?>> formParameterLocalVars = new List<KeyValuePair<string, string?>>();
 
                     if (enumFormString.IsSet)
@@ -4642,6 +4644,32 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
                     if (formParameterLocalVars.Count > 0)
                         httpRequestMessageLocalVar.Content = new FormUrlEncodedContent(formParameterLocalVars);
 
+                    if (enumHeaderString.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                    }
+
+                    if (enumHeaderStringArray.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string_array".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string_array"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                    }
+
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
                     string[] contentTypes = new string[] {
@@ -4882,10 +4910,28 @@ public async Task<ITestGroupParametersApiResponse> TestGroupParametersAsync(bool
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    // Set client side default value of Header Param "required_boolean_group".                    
+                    if (ClientUtils.IsContentHeader("required_boolean_group"))
+                    {
+                        httpRequestMessageLocalVar.Content?.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
+                    else
+                    {
+                        httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
 
                     if (booleanGroup.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                    {
+                      // Set client side default value of Header Param "boolean_group".                    
+                      if (ClientUtils.IsContentHeader("boolean_group"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5098,8 +5144,8 @@ public async Task<ITestInlineAdditionalPropertiesApiResponse> TestInlineAddition
                         ? "/fake/inline-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5311,8 +5357,8 @@ public async Task<ITestInlineFreeformAdditionalPropertiesApiResponse> TestInline
                         ? "/fake/inline-freeform-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-freeform-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(testInlineFreeformAdditionalPropertiesRequest, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -6037,8 +6083,8 @@ public async Task<ITestStringMapReferenceApiResponse> TestStringMapReferenceAsyn
                         ? "/fake/stringMap-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/stringMap-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index f3ac29a27b3f..980b7a0c1f89 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -279,8 +279,8 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
 
                     System.Collections.Specialized.NameValueCollection parseQueryStringLocalVar = System.Web.HttpUtility.ParseQueryString(string.Empty);
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/PetApi.cs
index c780f8623263..9d06e1ac4a9e 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/PetApi.cs
@@ -836,8 +836,8 @@ public async Task<IAddPetApiResponse> AddPetAsync(Pet pet, System.Threading.Canc
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
@@ -1085,7 +1085,17 @@ public async Task<IDeletePetApiResponse> DeletePetAsync(long petId, Option<strin
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7BpetId%7D", Uri.EscapeDataString(petId.ToString()));
 
                     if (apiKey.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                    {
+                      // Set client side default value of Header Param "api_key".                    
+                      if (ClientUtils.IsContentHeader("api_key"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2131,8 +2141,8 @@ public async Task<IUpdatePetApiResponse> UpdatePetAsync(Pet pet, System.Threadin
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/StoreApi.cs
index f357fb96d092..08624b36f6ad 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -1140,8 +1140,8 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         ? "/store/order"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/store/order");
 
-                    httpRequestMessageLocalVar.Content = (order as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (order as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(order, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/UserApi.cs
index da4e3661c441..c8536386fafb 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/UserApi.cs
@@ -714,8 +714,8 @@ public async Task<ICreateUserApiResponse> CreateUserAsync(User user, System.Thre
                         ? "/user"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -927,8 +927,8 @@ public async Task<ICreateUsersWithArrayInputApiResponse> CreateUsersWithArrayInp
                         ? "/user/createWithArray"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithArray");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -1140,8 +1140,8 @@ public async Task<ICreateUsersWithListInputApiResponse> CreateUsersWithListInput
                         ? "/user/createWithList"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithList");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2339,8 +2339,8 @@ public async Task<IUpdateUserApiResponse> UpdateUserAsync(User user, string user
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/{username}");
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7Busername%7D", Uri.EscapeDataString(username.ToString()));
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Client/ClientUtils.cs
index a66181bb5473..f442dd44bfa2 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -417,6 +417,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index e3f39f30bec8..64f0a9026639 100644
--- a/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -316,6 +316,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index 374598ad581f..0de8a13cdbd7 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -275,8 +275,8 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         ? "/another-fake/dummy"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/another-fake/dummy");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
index 271fbfea2636..46b99593f1d7 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -1602,9 +1602,11 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/boolean");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -1857,9 +1859,11 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/composite");
 
                     if (outerComposite.IsSet)
-                        httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2099,9 +2103,11 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/number");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2366,9 +2372,11 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -3274,8 +3282,8 @@ public async Task<ITestAdditionalPropertiesReferenceApiResponse> TestAdditionalP
                         ? "/fake/additionalProperties-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/additionalProperties-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3487,8 +3495,8 @@ public async Task<ITestBodyWithFileSchemaApiResponse> TestBodyWithFileSchemaAsyn
                         ? "/fake/body-with-file-schema"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/body-with-file-schema");
 
-                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(fileSchemaTestClass, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3716,8 +3724,8 @@ public async Task<ITestBodyWithQueryParamsApiResponse> TestBodyWithQueryParamsAs
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3929,8 +3937,8 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         ? "/fake"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -4623,12 +4631,6 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    if (enumHeaderString.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
-
-                    if (enumHeaderStringArray.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
-
                     List<KeyValuePair<string, string>> formParameterLocalVars = new List<KeyValuePair<string, string>>();
 
                     if (enumFormString.IsSet)
@@ -4640,6 +4642,32 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
                     if (formParameterLocalVars.Count > 0)
                         httpRequestMessageLocalVar.Content = new FormUrlEncodedContent(formParameterLocalVars);
 
+                    if (enumHeaderString.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                    }
+
+                    if (enumHeaderStringArray.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string_array".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string_array"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                    }
+
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
                     string[] contentTypes = new string[] {
@@ -4880,10 +4908,28 @@ public async Task<ITestGroupParametersApiResponse> TestGroupParametersAsync(bool
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    // Set client side default value of Header Param "required_boolean_group".                    
+                    if (ClientUtils.IsContentHeader("required_boolean_group"))
+                    {
+                        httpRequestMessageLocalVar.Content?.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
+                    else
+                    {
+                        httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
 
                     if (booleanGroup.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                    {
+                      // Set client side default value of Header Param "boolean_group".                    
+                      if (ClientUtils.IsContentHeader("boolean_group"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5096,8 +5142,8 @@ public async Task<ITestInlineAdditionalPropertiesApiResponse> TestInlineAddition
                         ? "/fake/inline-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5309,8 +5355,8 @@ public async Task<ITestInlineFreeformAdditionalPropertiesApiResponse> TestInline
                         ? "/fake/inline-freeform-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-freeform-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(testInlineFreeformAdditionalPropertiesRequest, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -6035,8 +6081,8 @@ public async Task<ITestStringMapReferenceApiResponse> TestStringMapReferenceAsyn
                         ? "/fake/stringMap-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/stringMap-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index 802d1fdb2ac1..2813dbef14b7 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -277,8 +277,8 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
 
                     System.Collections.Specialized.NameValueCollection parseQueryStringLocalVar = System.Web.HttpUtility.ParseQueryString(string.Empty);
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
index af5a07843603..0843443b2ae3 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
@@ -834,8 +834,8 @@ public async Task<IAddPetApiResponse> AddPetAsync(Pet pet, System.Threading.Canc
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
@@ -1083,7 +1083,17 @@ public async Task<IDeletePetApiResponse> DeletePetAsync(long petId, Option<strin
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7BpetId%7D", Uri.EscapeDataString(petId.ToString()));
 
                     if (apiKey.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                    {
+                      // Set client side default value of Header Param "api_key".                    
+                      if (ClientUtils.IsContentHeader("api_key"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2129,8 +2139,8 @@ public async Task<IUpdatePetApiResponse> UpdatePetAsync(Pet pet, System.Threadin
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
index 036a6d41dfa3..f05331998ad1 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -1138,8 +1138,8 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         ? "/store/order"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/store/order");
 
-                    httpRequestMessageLocalVar.Content = (order as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (order as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(order, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
index c6802990ffc6..ecdf56916766 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
@@ -712,8 +712,8 @@ public async Task<ICreateUserApiResponse> CreateUserAsync(User user, System.Thre
                         ? "/user"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -925,8 +925,8 @@ public async Task<ICreateUsersWithArrayInputApiResponse> CreateUsersWithArrayInp
                         ? "/user/createWithArray"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithArray");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -1138,8 +1138,8 @@ public async Task<ICreateUsersWithListInputApiResponse> CreateUsersWithListInput
                         ? "/user/createWithList"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithList");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2337,8 +2337,8 @@ public async Task<IUpdateUserApiResponse> UpdateUserAsync(User user, string user
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/{username}");
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7Busername%7D", Uri.EscapeDataString(username.ToString()));
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
index 3dfb7ecffbed..9ea7d8118c3b 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -415,6 +415,35 @@ public static string GetDiscriminator(Utf8JsonReader utf8JsonReader, string disc
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index e108a9106564..04b8da36fe38 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -277,8 +277,8 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         ? "/another-fake/dummy"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/another-fake/dummy");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/FakeApi.cs
index 7504f8b34bca..9242390191ce 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -1604,9 +1604,11 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/boolean");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -1859,9 +1861,11 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/composite");
 
                     if (outerComposite.IsSet)
-                        httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2101,9 +2105,11 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/number");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2368,9 +2374,11 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -3276,8 +3284,8 @@ public async Task<ITestAdditionalPropertiesReferenceApiResponse> TestAdditionalP
                         ? "/fake/additionalProperties-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/additionalProperties-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3489,8 +3497,8 @@ public async Task<ITestBodyWithFileSchemaApiResponse> TestBodyWithFileSchemaAsyn
                         ? "/fake/body-with-file-schema"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/body-with-file-schema");
 
-                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(fileSchemaTestClass, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3718,8 +3726,8 @@ public async Task<ITestBodyWithQueryParamsApiResponse> TestBodyWithQueryParamsAs
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3931,8 +3939,8 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         ? "/fake"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -4625,12 +4633,6 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    if (enumHeaderString.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
-
-                    if (enumHeaderStringArray.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
-
                     List<KeyValuePair<string, string?>> formParameterLocalVars = new List<KeyValuePair<string, string?>>();
 
                     if (enumFormString.IsSet)
@@ -4642,6 +4644,32 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
                     if (formParameterLocalVars.Count > 0)
                         httpRequestMessageLocalVar.Content = new FormUrlEncodedContent(formParameterLocalVars);
 
+                    if (enumHeaderString.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                    }
+
+                    if (enumHeaderStringArray.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string_array".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string_array"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                    }
+
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
                     string[] contentTypes = new string[] {
@@ -4882,10 +4910,28 @@ public async Task<ITestGroupParametersApiResponse> TestGroupParametersAsync(bool
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    // Set client side default value of Header Param "required_boolean_group".                    
+                    if (ClientUtils.IsContentHeader("required_boolean_group"))
+                    {
+                        httpRequestMessageLocalVar.Content?.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
+                    else
+                    {
+                        httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
 
                     if (booleanGroup.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                    {
+                      // Set client side default value of Header Param "boolean_group".                    
+                      if (ClientUtils.IsContentHeader("boolean_group"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5098,8 +5144,8 @@ public async Task<ITestInlineAdditionalPropertiesApiResponse> TestInlineAddition
                         ? "/fake/inline-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5311,8 +5357,8 @@ public async Task<ITestInlineFreeformAdditionalPropertiesApiResponse> TestInline
                         ? "/fake/inline-freeform-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-freeform-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(testInlineFreeformAdditionalPropertiesRequest, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -6037,8 +6083,8 @@ public async Task<ITestStringMapReferenceApiResponse> TestStringMapReferenceAsyn
                         ? "/fake/stringMap-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/stringMap-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index f3ac29a27b3f..980b7a0c1f89 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -279,8 +279,8 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
 
                     System.Collections.Specialized.NameValueCollection parseQueryStringLocalVar = System.Web.HttpUtility.ParseQueryString(string.Empty);
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/PetApi.cs
index c780f8623263..9d06e1ac4a9e 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/PetApi.cs
@@ -836,8 +836,8 @@ public async Task<IAddPetApiResponse> AddPetAsync(Pet pet, System.Threading.Canc
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
@@ -1085,7 +1085,17 @@ public async Task<IDeletePetApiResponse> DeletePetAsync(long petId, Option<strin
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7BpetId%7D", Uri.EscapeDataString(petId.ToString()));
 
                     if (apiKey.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                    {
+                      // Set client side default value of Header Param "api_key".                    
+                      if (ClientUtils.IsContentHeader("api_key"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2131,8 +2141,8 @@ public async Task<IUpdatePetApiResponse> UpdatePetAsync(Pet pet, System.Threadin
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/StoreApi.cs
index f357fb96d092..08624b36f6ad 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -1140,8 +1140,8 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         ? "/store/order"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/store/order");
 
-                    httpRequestMessageLocalVar.Content = (order as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (order as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(order, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/UserApi.cs
index da4e3661c441..c8536386fafb 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/UserApi.cs
@@ -714,8 +714,8 @@ public async Task<ICreateUserApiResponse> CreateUserAsync(User user, System.Thre
                         ? "/user"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -927,8 +927,8 @@ public async Task<ICreateUsersWithArrayInputApiResponse> CreateUsersWithArrayInp
                         ? "/user/createWithArray"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithArray");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -1140,8 +1140,8 @@ public async Task<ICreateUsersWithListInputApiResponse> CreateUsersWithListInput
                         ? "/user/createWithList"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithList");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2339,8 +2339,8 @@ public async Task<IUpdateUserApiResponse> UpdateUserAsync(User user, string user
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/{username}");
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7Busername%7D", Uri.EscapeDataString(username.ToString()));
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Client/ClientUtils.cs
index a66181bb5473..f442dd44bfa2 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -417,6 +417,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
index 55d79ce4b6a8..3310db6b99d8 100644
--- a/samples/client/petstore/csharp/generichost/net8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -301,6 +301,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net9/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net9/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index c75a26cd1562..2157bc68a4f5 100644
--- a/samples/client/petstore/csharp/generichost/net9/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net9/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -316,6 +316,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index e3f39f30bec8..64f0a9026639 100644
--- a/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -316,6 +316,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
index 0efabe7ad9a2..4da07961deed 100644
--- a/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -301,6 +301,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index 374598ad581f..0de8a13cdbd7 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -275,8 +275,8 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         ? "/another-fake/dummy"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/another-fake/dummy");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
index 8a489ed1f3f3..6638ec4068d1 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -1602,9 +1602,11 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/boolean");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -1857,9 +1859,11 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/composite");
 
                     if (outerComposite.IsSet)
-                        httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2099,9 +2103,11 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/number");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2366,9 +2372,11 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -3274,8 +3282,8 @@ public async Task<ITestAdditionalPropertiesReferenceApiResponse> TestAdditionalP
                         ? "/fake/additionalProperties-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/additionalProperties-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3487,8 +3495,8 @@ public async Task<ITestBodyWithFileSchemaApiResponse> TestBodyWithFileSchemaAsyn
                         ? "/fake/body-with-file-schema"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/body-with-file-schema");
 
-                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(fileSchemaTestClass, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3716,8 +3724,8 @@ public async Task<ITestBodyWithQueryParamsApiResponse> TestBodyWithQueryParamsAs
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3929,8 +3937,8 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         ? "/fake"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -4611,12 +4619,6 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    if (enumHeaderString.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
-
-                    if (enumHeaderStringArray.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
-
                     List<KeyValuePair<string, string>> formParameterLocalVars = new List<KeyValuePair<string, string>>();
 
                     if (enumFormString.IsSet)
@@ -4628,6 +4630,32 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
                     if (formParameterLocalVars.Count > 0)
                         httpRequestMessageLocalVar.Content = new FormUrlEncodedContent(formParameterLocalVars);
 
+                    if (enumHeaderString.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                    }
+
+                    if (enumHeaderStringArray.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string_array".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string_array"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                    }
+
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
                     string[] contentTypes = new string[] {
@@ -4868,10 +4896,28 @@ public async Task<ITestGroupParametersApiResponse> TestGroupParametersAsync(bool
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    // Set client side default value of Header Param "required_boolean_group".                    
+                    if (ClientUtils.IsContentHeader("required_boolean_group"))
+                    {
+                        httpRequestMessageLocalVar.Content?.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
+                    else
+                    {
+                        httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
 
                     if (booleanGroup.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                    {
+                      // Set client side default value of Header Param "boolean_group".                    
+                      if (ClientUtils.IsContentHeader("boolean_group"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5084,8 +5130,8 @@ public async Task<ITestInlineAdditionalPropertiesApiResponse> TestInlineAddition
                         ? "/fake/inline-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5297,8 +5343,8 @@ public async Task<ITestInlineFreeformAdditionalPropertiesApiResponse> TestInline
                         ? "/fake/inline-freeform-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-freeform-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(testInlineFreeformAdditionalPropertiesRequest, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -6023,8 +6069,8 @@ public async Task<ITestStringMapReferenceApiResponse> TestStringMapReferenceAsyn
                         ? "/fake/stringMap-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/stringMap-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index 802d1fdb2ac1..2813dbef14b7 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -277,8 +277,8 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
 
                     System.Collections.Specialized.NameValueCollection parseQueryStringLocalVar = System.Web.HttpUtility.ParseQueryString(string.Empty);
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
index 47c89d10aaa9..7a052a90d955 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
@@ -834,8 +834,8 @@ public async Task<IAddPetApiResponse> AddPetAsync(Pet pet, System.Threading.Canc
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
@@ -1083,7 +1083,17 @@ public async Task<IDeletePetApiResponse> DeletePetAsync(long petId, Option<strin
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7BpetId%7D", Uri.EscapeDataString(petId.ToString()));
 
                     if (apiKey.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                    {
+                      // Set client side default value of Header Param "api_key".                    
+                      if (ClientUtils.IsContentHeader("api_key"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2129,8 +2139,8 @@ public async Task<IUpdatePetApiResponse> UpdatePetAsync(Pet pet, System.Threadin
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
index 036a6d41dfa3..f05331998ad1 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -1138,8 +1138,8 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         ? "/store/order"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/store/order");
 
-                    httpRequestMessageLocalVar.Content = (order as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (order as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(order, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
index c6802990ffc6..ecdf56916766 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
@@ -712,8 +712,8 @@ public async Task<ICreateUserApiResponse> CreateUserAsync(User user, System.Thre
                         ? "/user"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -925,8 +925,8 @@ public async Task<ICreateUsersWithArrayInputApiResponse> CreateUsersWithArrayInp
                         ? "/user/createWithArray"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithArray");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -1138,8 +1138,8 @@ public async Task<ICreateUsersWithListInputApiResponse> CreateUsersWithListInput
                         ? "/user/createWithList"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithList");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2337,8 +2337,8 @@ public async Task<IUpdateUserApiResponse> UpdateUserAsync(User user, string user
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/{username}");
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7Busername%7D", Uri.EscapeDataString(username.ToString()));
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
index 97b8745cc47b..be99808e8e53 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -411,6 +411,35 @@ public static string GetDiscriminator(Utf8JsonReader utf8JsonReader, string disc
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index e108a9106564..04b8da36fe38 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -277,8 +277,8 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         ? "/another-fake/dummy"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/another-fake/dummy");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeApi.cs
index 7504f8b34bca..9242390191ce 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -1604,9 +1604,11 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/boolean");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -1859,9 +1861,11 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/composite");
 
                     if (outerComposite.IsSet)
-                        httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2101,9 +2105,11 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/number");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2368,9 +2374,11 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -3276,8 +3284,8 @@ public async Task<ITestAdditionalPropertiesReferenceApiResponse> TestAdditionalP
                         ? "/fake/additionalProperties-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/additionalProperties-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3489,8 +3497,8 @@ public async Task<ITestBodyWithFileSchemaApiResponse> TestBodyWithFileSchemaAsyn
                         ? "/fake/body-with-file-schema"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/body-with-file-schema");
 
-                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(fileSchemaTestClass, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3718,8 +3726,8 @@ public async Task<ITestBodyWithQueryParamsApiResponse> TestBodyWithQueryParamsAs
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3931,8 +3939,8 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         ? "/fake"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -4625,12 +4633,6 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    if (enumHeaderString.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
-
-                    if (enumHeaderStringArray.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
-
                     List<KeyValuePair<string, string?>> formParameterLocalVars = new List<KeyValuePair<string, string?>>();
 
                     if (enumFormString.IsSet)
@@ -4642,6 +4644,32 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
                     if (formParameterLocalVars.Count > 0)
                         httpRequestMessageLocalVar.Content = new FormUrlEncodedContent(formParameterLocalVars);
 
+                    if (enumHeaderString.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                    }
+
+                    if (enumHeaderStringArray.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string_array".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string_array"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                    }
+
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
                     string[] contentTypes = new string[] {
@@ -4882,10 +4910,28 @@ public async Task<ITestGroupParametersApiResponse> TestGroupParametersAsync(bool
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    // Set client side default value of Header Param "required_boolean_group".                    
+                    if (ClientUtils.IsContentHeader("required_boolean_group"))
+                    {
+                        httpRequestMessageLocalVar.Content?.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
+                    else
+                    {
+                        httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
 
                     if (booleanGroup.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                    {
+                      // Set client side default value of Header Param "boolean_group".                    
+                      if (ClientUtils.IsContentHeader("boolean_group"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5098,8 +5144,8 @@ public async Task<ITestInlineAdditionalPropertiesApiResponse> TestInlineAddition
                         ? "/fake/inline-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5311,8 +5357,8 @@ public async Task<ITestInlineFreeformAdditionalPropertiesApiResponse> TestInline
                         ? "/fake/inline-freeform-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-freeform-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(testInlineFreeformAdditionalPropertiesRequest, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -6037,8 +6083,8 @@ public async Task<ITestStringMapReferenceApiResponse> TestStringMapReferenceAsyn
                         ? "/fake/stringMap-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/stringMap-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index f3ac29a27b3f..980b7a0c1f89 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -279,8 +279,8 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
 
                     System.Collections.Specialized.NameValueCollection parseQueryStringLocalVar = System.Web.HttpUtility.ParseQueryString(string.Empty);
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/PetApi.cs
index c780f8623263..9d06e1ac4a9e 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/PetApi.cs
@@ -836,8 +836,8 @@ public async Task<IAddPetApiResponse> AddPetAsync(Pet pet, System.Threading.Canc
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
@@ -1085,7 +1085,17 @@ public async Task<IDeletePetApiResponse> DeletePetAsync(long petId, Option<strin
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7BpetId%7D", Uri.EscapeDataString(petId.ToString()));
 
                     if (apiKey.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                    {
+                      // Set client side default value of Header Param "api_key".                    
+                      if (ClientUtils.IsContentHeader("api_key"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2131,8 +2141,8 @@ public async Task<IUpdatePetApiResponse> UpdatePetAsync(Pet pet, System.Threadin
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/StoreApi.cs
index f357fb96d092..08624b36f6ad 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -1140,8 +1140,8 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         ? "/store/order"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/store/order");
 
-                    httpRequestMessageLocalVar.Content = (order as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (order as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(order, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/UserApi.cs
index da4e3661c441..c8536386fafb 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/UserApi.cs
@@ -714,8 +714,8 @@ public async Task<ICreateUserApiResponse> CreateUserAsync(User user, System.Thre
                         ? "/user"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -927,8 +927,8 @@ public async Task<ICreateUsersWithArrayInputApiResponse> CreateUsersWithArrayInp
                         ? "/user/createWithArray"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithArray");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -1140,8 +1140,8 @@ public async Task<ICreateUsersWithListInputApiResponse> CreateUsersWithListInput
                         ? "/user/createWithList"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithList");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2339,8 +2339,8 @@ public async Task<IUpdateUserApiResponse> UpdateUserAsync(User user, string user
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/{username}");
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7Busername%7D", Uri.EscapeDataString(username.ToString()));
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Client/ClientUtils.cs
index a66181bb5473..f442dd44bfa2 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -417,6 +417,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index e3f39f30bec8..64f0a9026639 100644
--- a/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -316,6 +316,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index 374598ad581f..0de8a13cdbd7 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -275,8 +275,8 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         ? "/another-fake/dummy"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/another-fake/dummy");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
index 271fbfea2636..46b99593f1d7 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -1602,9 +1602,11 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/boolean");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -1857,9 +1859,11 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/composite");
 
                     if (outerComposite.IsSet)
-                        httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2099,9 +2103,11 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/number");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2366,9 +2372,11 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -3274,8 +3282,8 @@ public async Task<ITestAdditionalPropertiesReferenceApiResponse> TestAdditionalP
                         ? "/fake/additionalProperties-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/additionalProperties-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3487,8 +3495,8 @@ public async Task<ITestBodyWithFileSchemaApiResponse> TestBodyWithFileSchemaAsyn
                         ? "/fake/body-with-file-schema"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/body-with-file-schema");
 
-                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(fileSchemaTestClass, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3716,8 +3724,8 @@ public async Task<ITestBodyWithQueryParamsApiResponse> TestBodyWithQueryParamsAs
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3929,8 +3937,8 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         ? "/fake"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -4623,12 +4631,6 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    if (enumHeaderString.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
-
-                    if (enumHeaderStringArray.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
-
                     List<KeyValuePair<string, string>> formParameterLocalVars = new List<KeyValuePair<string, string>>();
 
                     if (enumFormString.IsSet)
@@ -4640,6 +4642,32 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
                     if (formParameterLocalVars.Count > 0)
                         httpRequestMessageLocalVar.Content = new FormUrlEncodedContent(formParameterLocalVars);
 
+                    if (enumHeaderString.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                    }
+
+                    if (enumHeaderStringArray.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string_array".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string_array"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                    }
+
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
                     string[] contentTypes = new string[] {
@@ -4880,10 +4908,28 @@ public async Task<ITestGroupParametersApiResponse> TestGroupParametersAsync(bool
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    // Set client side default value of Header Param "required_boolean_group".                    
+                    if (ClientUtils.IsContentHeader("required_boolean_group"))
+                    {
+                        httpRequestMessageLocalVar.Content?.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
+                    else
+                    {
+                        httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
 
                     if (booleanGroup.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                    {
+                      // Set client side default value of Header Param "boolean_group".                    
+                      if (ClientUtils.IsContentHeader("boolean_group"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5096,8 +5142,8 @@ public async Task<ITestInlineAdditionalPropertiesApiResponse> TestInlineAddition
                         ? "/fake/inline-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5309,8 +5355,8 @@ public async Task<ITestInlineFreeformAdditionalPropertiesApiResponse> TestInline
                         ? "/fake/inline-freeform-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-freeform-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(testInlineFreeformAdditionalPropertiesRequest, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -6035,8 +6081,8 @@ public async Task<ITestStringMapReferenceApiResponse> TestStringMapReferenceAsyn
                         ? "/fake/stringMap-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/stringMap-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index 802d1fdb2ac1..2813dbef14b7 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -277,8 +277,8 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
 
                     System.Collections.Specialized.NameValueCollection parseQueryStringLocalVar = System.Web.HttpUtility.ParseQueryString(string.Empty);
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
index af5a07843603..0843443b2ae3 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
@@ -834,8 +834,8 @@ public async Task<IAddPetApiResponse> AddPetAsync(Pet pet, System.Threading.Canc
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
@@ -1083,7 +1083,17 @@ public async Task<IDeletePetApiResponse> DeletePetAsync(long petId, Option<strin
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7BpetId%7D", Uri.EscapeDataString(petId.ToString()));
 
                     if (apiKey.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                    {
+                      // Set client side default value of Header Param "api_key".                    
+                      if (ClientUtils.IsContentHeader("api_key"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2129,8 +2139,8 @@ public async Task<IUpdatePetApiResponse> UpdatePetAsync(Pet pet, System.Threadin
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
index 036a6d41dfa3..f05331998ad1 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -1138,8 +1138,8 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         ? "/store/order"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/store/order");
 
-                    httpRequestMessageLocalVar.Content = (order as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (order as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(order, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
index c6802990ffc6..ecdf56916766 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
@@ -712,8 +712,8 @@ public async Task<ICreateUserApiResponse> CreateUserAsync(User user, System.Thre
                         ? "/user"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -925,8 +925,8 @@ public async Task<ICreateUsersWithArrayInputApiResponse> CreateUsersWithArrayInp
                         ? "/user/createWithArray"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithArray");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -1138,8 +1138,8 @@ public async Task<ICreateUsersWithListInputApiResponse> CreateUsersWithListInput
                         ? "/user/createWithList"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithList");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2337,8 +2337,8 @@ public async Task<IUpdateUserApiResponse> UpdateUserAsync(User user, string user
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/{username}");
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7Busername%7D", Uri.EscapeDataString(username.ToString()));
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
index 3dfb7ecffbed..9ea7d8118c3b 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -415,6 +415,35 @@ public static string GetDiscriminator(Utf8JsonReader utf8JsonReader, string disc
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index e108a9106564..04b8da36fe38 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -277,8 +277,8 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         ? "/another-fake/dummy"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/another-fake/dummy");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/FakeApi.cs
index 7504f8b34bca..9242390191ce 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -1604,9 +1604,11 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/boolean");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -1859,9 +1861,11 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/composite");
 
                     if (outerComposite.IsSet)
-                        httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2101,9 +2105,11 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/number");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2368,9 +2374,11 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -3276,8 +3284,8 @@ public async Task<ITestAdditionalPropertiesReferenceApiResponse> TestAdditionalP
                         ? "/fake/additionalProperties-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/additionalProperties-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3489,8 +3497,8 @@ public async Task<ITestBodyWithFileSchemaApiResponse> TestBodyWithFileSchemaAsyn
                         ? "/fake/body-with-file-schema"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/body-with-file-schema");
 
-                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(fileSchemaTestClass, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3718,8 +3726,8 @@ public async Task<ITestBodyWithQueryParamsApiResponse> TestBodyWithQueryParamsAs
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3931,8 +3939,8 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         ? "/fake"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -4625,12 +4633,6 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    if (enumHeaderString.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
-
-                    if (enumHeaderStringArray.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
-
                     List<KeyValuePair<string, string?>> formParameterLocalVars = new List<KeyValuePair<string, string?>>();
 
                     if (enumFormString.IsSet)
@@ -4642,6 +4644,32 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
                     if (formParameterLocalVars.Count > 0)
                         httpRequestMessageLocalVar.Content = new FormUrlEncodedContent(formParameterLocalVars);
 
+                    if (enumHeaderString.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                    }
+
+                    if (enumHeaderStringArray.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string_array".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string_array"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                    }
+
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
                     string[] contentTypes = new string[] {
@@ -4882,10 +4910,28 @@ public async Task<ITestGroupParametersApiResponse> TestGroupParametersAsync(bool
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    // Set client side default value of Header Param "required_boolean_group".                    
+                    if (ClientUtils.IsContentHeader("required_boolean_group"))
+                    {
+                        httpRequestMessageLocalVar.Content?.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
+                    else
+                    {
+                        httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
 
                     if (booleanGroup.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                    {
+                      // Set client side default value of Header Param "boolean_group".                    
+                      if (ClientUtils.IsContentHeader("boolean_group"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5098,8 +5144,8 @@ public async Task<ITestInlineAdditionalPropertiesApiResponse> TestInlineAddition
                         ? "/fake/inline-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5311,8 +5357,8 @@ public async Task<ITestInlineFreeformAdditionalPropertiesApiResponse> TestInline
                         ? "/fake/inline-freeform-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-freeform-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(testInlineFreeformAdditionalPropertiesRequest, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -6037,8 +6083,8 @@ public async Task<ITestStringMapReferenceApiResponse> TestStringMapReferenceAsyn
                         ? "/fake/stringMap-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/stringMap-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index f3ac29a27b3f..980b7a0c1f89 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -279,8 +279,8 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
 
                     System.Collections.Specialized.NameValueCollection parseQueryStringLocalVar = System.Web.HttpUtility.ParseQueryString(string.Empty);
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/PetApi.cs
index c780f8623263..9d06e1ac4a9e 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/PetApi.cs
@@ -836,8 +836,8 @@ public async Task<IAddPetApiResponse> AddPetAsync(Pet pet, System.Threading.Canc
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
@@ -1085,7 +1085,17 @@ public async Task<IDeletePetApiResponse> DeletePetAsync(long petId, Option<strin
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7BpetId%7D", Uri.EscapeDataString(petId.ToString()));
 
                     if (apiKey.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                    {
+                      // Set client side default value of Header Param "api_key".                    
+                      if (ClientUtils.IsContentHeader("api_key"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2131,8 +2141,8 @@ public async Task<IUpdatePetApiResponse> UpdatePetAsync(Pet pet, System.Threadin
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/StoreApi.cs
index f357fb96d092..08624b36f6ad 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -1140,8 +1140,8 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         ? "/store/order"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/store/order");
 
-                    httpRequestMessageLocalVar.Content = (order as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (order as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(order, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/UserApi.cs
index da4e3661c441..c8536386fafb 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/UserApi.cs
@@ -714,8 +714,8 @@ public async Task<ICreateUserApiResponse> CreateUserAsync(User user, System.Thre
                         ? "/user"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -927,8 +927,8 @@ public async Task<ICreateUsersWithArrayInputApiResponse> CreateUsersWithArrayInp
                         ? "/user/createWithArray"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithArray");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -1140,8 +1140,8 @@ public async Task<ICreateUsersWithListInputApiResponse> CreateUsersWithListInput
                         ? "/user/createWithList"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithList");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2339,8 +2339,8 @@ public async Task<IUpdateUserApiResponse> UpdateUserAsync(User user, string user
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/{username}");
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7Busername%7D", Uri.EscapeDataString(username.ToString()));
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Client/ClientUtils.cs
index a66181bb5473..f442dd44bfa2 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -417,6 +417,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net9/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net9/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
index 55d79ce4b6a8..3310db6b99d8 100644
--- a/samples/client/petstore/csharp/generichost/net9/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net9/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -301,6 +301,35 @@ public static bool IsJsonMime(string mime)
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index d5ef07d0af6c..6eb8990489ae 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -274,8 +274,8 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         ? "/another-fake/dummy"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/another-fake/dummy");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
index 0cde2825a8f0..7f78296b1c0b 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -1600,9 +1600,11 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/boolean");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -1854,9 +1856,11 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/composite");
 
                     if (outerComposite.IsSet)
-                        httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (outerComposite.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(outerComposite.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2095,9 +2099,11 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/outer/number");
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -2361,9 +2367,11 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
                     if (body.IsSet)
-                        httpRequestMessageLocalVar.Content = (body.Value as object) is System.IO.Stream stream
-                            ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
-                            : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    {
+                      httpRequestMessageLocalVar.Content = (body.Value as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
+                        : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(body.Value, _jsonSerializerOptions));
+                    }
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
@@ -3265,8 +3273,8 @@ public async Task<ITestAdditionalPropertiesReferenceApiResponse> TestAdditionalP
                         ? "/fake/additionalProperties-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/additionalProperties-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3478,8 +3486,8 @@ public async Task<ITestBodyWithFileSchemaApiResponse> TestBodyWithFileSchemaAsyn
                         ? "/fake/body-with-file-schema"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/body-with-file-schema");
 
-                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (fileSchemaTestClass as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(fileSchemaTestClass, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3707,8 +3715,8 @@ public async Task<ITestBodyWithQueryParamsApiResponse> TestBodyWithQueryParamsAs
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -3920,8 +3928,8 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         ? "/fake"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake");
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -4613,12 +4621,6 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    if (enumHeaderString.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
-
-                    if (enumHeaderStringArray.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
-
                     List<KeyValuePair<string, string>> formParameterLocalVars = new List<KeyValuePair<string, string>>();
 
                     if (enumFormString.IsSet)
@@ -4630,6 +4632,32 @@ public async Task<ITestEnumParametersApiResponse> TestEnumParametersAsync(Option
                     if (formParameterLocalVars.Count > 0)
                         httpRequestMessageLocalVar.Content = new FormUrlEncodedContent(formParameterLocalVars);
 
+                    if (enumHeaderString.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string", ClientUtils.ParameterToString(enumHeaderString.Value));
+                      }
+                    }
+
+                    if (enumHeaderStringArray.IsSet)
+                    {
+                      // Set client side default value of Header Param "enum_header_string_array".                    
+                      if (ClientUtils.IsContentHeader("enum_header_string_array"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("enum_header_string_array", ClientUtils.ParameterToString(enumHeaderStringArray.Value));
+                      }
+                    }
+
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
 
                     string[] contentTypes = new string[] {
@@ -4870,10 +4898,28 @@ public async Task<ITestGroupParametersApiResponse> TestGroupParametersAsync(bool
 
                     uriBuilderLocalVar.Query = parseQueryStringLocalVar.ToString();
 
-                    httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    // Set client side default value of Header Param "required_boolean_group".                    
+                    if (ClientUtils.IsContentHeader("required_boolean_group"))
+                    {
+                        httpRequestMessageLocalVar.Content?.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
+                    else
+                    {
+                        httpRequestMessageLocalVar.Headers.Add("required_boolean_group", ClientUtils.ParameterToString(requiredBooleanGroup));
+                    }
 
                     if (booleanGroup.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                    {
+                      // Set client side default value of Header Param "boolean_group".                    
+                      if (ClientUtils.IsContentHeader("boolean_group"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("boolean_group", ClientUtils.ParameterToString(booleanGroup.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5085,8 +5131,8 @@ public async Task<ITestInlineAdditionalPropertiesApiResponse> TestInlineAddition
                         ? "/fake/inline-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -5298,8 +5344,8 @@ public async Task<ITestInlineFreeformAdditionalPropertiesApiResponse> TestInline
                         ? "/fake/inline-freeform-additionalProperties"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/inline-freeform-additionalProperties");
 
-                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (testInlineFreeformAdditionalPropertiesRequest as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(testInlineFreeformAdditionalPropertiesRequest, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -6023,8 +6069,8 @@ public async Task<ITestStringMapReferenceApiResponse> TestStringMapReferenceAsyn
                         ? "/fake/stringMap-reference"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/fake/stringMap-reference");
 
-                    httpRequestMessageLocalVar.Content = (requestBody as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (requestBody as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(requestBody, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index 3513619a880c..c84e52a5a500 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -276,8 +276,8 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
 
                     System.Collections.Specialized.NameValueCollection parseQueryStringLocalVar = System.Web.HttpUtility.ParseQueryString(string.Empty);
 
-                    httpRequestMessageLocalVar.Content = (modelClient as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (modelClient as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(modelClient, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
index 7592e4b8d2fd..8fd9ec7fe213 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
@@ -833,8 +833,8 @@ public async Task<IAddPetApiResponse> AddPetAsync(Pet pet, System.Threading.Canc
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
@@ -1082,7 +1082,17 @@ public async Task<IDeletePetApiResponse> DeletePetAsync(long petId, Option<strin
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7BpetId%7D", Uri.EscapeDataString(petId.ToString()));
 
                     if (apiKey.IsSet)
-                        httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                    {
+                      // Set client side default value of Header Param "api_key".                    
+                      if (ClientUtils.IsContentHeader("api_key"))
+                      {
+                          httpRequestMessageLocalVar.Content?.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                      else
+                      {
+                          httpRequestMessageLocalVar.Headers.Add("api_key", ClientUtils.ParameterToString(apiKey.Value));
+                      }
+                    }
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2124,8 +2134,8 @@ public async Task<IUpdatePetApiResponse> UpdatePetAsync(Pet pet, System.Threadin
                     uriBuilderLocalVar.Scheme = urlLocalVar.Scheme;
                     uriBuilderLocalVar.Path = urlLocalVar.AbsolutePath;
 
-                    httpRequestMessageLocalVar.Content = (pet as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (pet as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(pet, _jsonSerializerOptions));
 
                     List<TokenBase> tokenBaseLocalVars = new List<TokenBase>();
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
index 7c748b85f522..f8551cfa6d00 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -1134,8 +1134,8 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         ? "/store/order"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/store/order");
 
-                    httpRequestMessageLocalVar.Content = (order as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (order as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(order, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
index 4f5e5922505b..6f79c82446ac 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
@@ -703,8 +703,8 @@ public async Task<ICreateUserApiResponse> CreateUserAsync(User user, System.Thre
                         ? "/user"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -916,8 +916,8 @@ public async Task<ICreateUsersWithArrayInputApiResponse> CreateUsersWithArrayInp
                         ? "/user/createWithArray"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithArray");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -1129,8 +1129,8 @@ public async Task<ICreateUsersWithListInputApiResponse> CreateUsersWithListInput
                         ? "/user/createWithList"
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/createWithList");
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
@@ -2297,8 +2297,8 @@ public async Task<IUpdateUserApiResponse> UpdateUserAsync(User user, string user
                         : string.Concat(HttpClient.BaseAddress.AbsolutePath.TrimEnd('/'), "/user/{username}");
                     uriBuilderLocalVar.Path = uriBuilderLocalVar.Path.Replace("%7Busername%7D", Uri.EscapeDataString(username.ToString()));
 
-                    httpRequestMessageLocalVar.Content = (user as object) is System.IO.Stream stream
-                        ? httpRequestMessageLocalVar.Content = new StreamContent(stream)
+                    httpRequestMessageLocalVar.Content = (user as object) is Org.OpenAPITools.Client.FileParameter fileParameterLocalVar
+                        ? httpRequestMessageLocalVar.Content = new StreamContent(fileParameterLocalVar.Content)
                         : httpRequestMessageLocalVar.Content = new StringContent(JsonSerializer.Serialize(user, _jsonSerializerOptions));
 
                     httpRequestMessageLocalVar.RequestUri = uriBuilderLocalVar.Uri;
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
index c2d90fee7b00..92d95ba94060 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -415,6 +415,35 @@ public static string GetDiscriminator(Utf8JsonReader utf8JsonReader, string disc
             throw new JsonException("The specified discriminator was not found.");
         }
 
+        /// <summary>
+        /// Determines if the provided header is a content header
+        /// </summary>
+        /// <param name="header">The header to check</param>
+        /// <returns>True if a content header; False otherwise</returns>
+        public static bool IsContentHeader(string header)
+        {
+            return ContentHeaders.Contains(header.ToLowerInvariant());
+        }
+
+        /// <summary>
+        /// The collection of content headers as per
+        /// https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpcontent.headers
+        /// </summary>
+        private static readonly string[] ContentHeaders = new String[] 
+        {
+            "allow",
+            "content-encoding",
+            "content-disposition",
+            "content-language",
+            "content-length",
+            "content-location",
+            "content-md5",
+            "content-range",
+            "content-type",
+            "expires",
+            "last-modified"
+        };
+
         /// <summary>
         /// The base path of the API
         /// </summary>