Add support for other Accept header values or full arrays when multiple options are present.

Author: EraYaN

modules/openapi-generator/src/main/resources/csharp/libraries/generichost/ClientUtils.mustache

@@ -18,6 +18,7 @@ using {{packageName}}.{{modelPackage}};
 {{/-first}}
 {{/models}}
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 {{>Assembly}}namespace {{packageName}}.{{clientPackage}}
 {
@@ -311,6 +312,26 @@ using System.Runtime.CompilerServices;
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                return null;
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                return [MediaTypeWithQualityHeaderValue.Parse("application/json")];
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>

modules/openapi-generator/src/main/resources/csharp/libraries/generichost/api.mustache

@@ -8,6 +8,7 @@
 {{/nrt}}
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 {{#net80OrLater}}
 {{#lambda.uniqueLines}}
 {{#operations}}
@@ -20,6 +21,7 @@ using System.Linq;
 {{/lambda.uniqueLines}}
 {{/net80OrLater}}
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -605,10 +607,10 @@ namespace {{packageName}}.{{apiPackage}}
                     {{#produces}}
                     {{#-first}}
 
-                    string{{nrt?}} acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     {{/-first}}
                     {{/produces}}
                     {{#net60OrLater}}