Return FileResult type for binary response if an AspNetCore controlle…

…r is generated (RicoSuter#2376)

* Return FileResult type for binary response if an AspNetCore controller is generated

* optimalization

src/NSwag.CodeGeneration.CSharp/CSharpGeneratorBase.cs

@@ -56,6 +56,21 @@ public override string GetTypeName(JsonSchema schema, bool isNullable, string ty
                 .Replace(_settings.CSharpGeneratorSettings.DictionaryType + "<", _settings.ResponseDictionaryType + "<");
         }
 
+        /// <summary>
+        /// Gets name of type for binary response
+        /// </summary>
+        /// <returns>FileResponse by default, FileResult if ControllerTarger parameter is AspNetCore</returns>
+        public override string GetBinaryResponseTypeName()
+        {
+            if (_settings is CSharpControllerGeneratorSettings controllerSettings 
+                && controllerSettings.ControllerTarget == CSharpControllerTarget.AspNetCore)
+            {
+                return "FileResult";
+            }
+
+            return base.GetBinaryResponseTypeName();
+        }
+
         /// <summary>Creates a new resolver, adds the given schema definitions and registers an exception schema if available.</summary>
         /// <param name="settings">The settings.</param>
         /// <param name="document">The document </param>