Revive call to FormattingUtilities in XmlDataContractSerializerOutputFormatter

Fixes #6235

src/Microsoft.AspNetCore.Mvc.Formatters.Xml/XmlDataContractSerializerOutputFormatter.cs

@@ -132,7 +132,9 @@ namespace Microsoft.AspNetCore.Mvc.Formatters
 
             try
             {
-                // Use FormattingUtilities here when https://github.com/aspnet/Mvc/issues/6235 is resolved.
+                // Verify that type is a valid data contract by forcing the serializer to try to create a data contract
+                FormattingUtilities.XsdDataContractExporter.GetRootElementName(type);
+
                 // If the serializer does not support this type it will throw an exception.
                 return new DataContractSerializer(type, _serializerSettings);
             }

test/Microsoft.AspNetCore.Mvc.FunctionalTests/ApiExplorerTest.cs

@@ -1,8 +1,9 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-using System.Linq;
 using System.Collections.Generic;
+using System.Linq;
+using System.Net;
 using System.Net.Http;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Mvc.Formatters;
@@ -10,8 +11,6 @@ using Microsoft.AspNetCore.Mvc.ModelBinding;
 using Microsoft.AspNetCore.Testing.xunit;
 using Newtonsoft.Json;
 using Xunit;
-using Microsoft.AspNetCore.Http;
-using System.Net;
 
 namespace Microsoft.AspNetCore.Mvc.FunctionalTests
 {
@@ -571,7 +570,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         {
             // Arrange
             var type1 = typeof(ApiExplorerWebSite.Product).FullName;
-            var type2 = typeof(ModelStateDictionary).FullName;
+            var type2 = typeof(SerializableError).FullName;
             var expectedMediaTypes = new[] { "application/json", "text/json", "application/xml", "text/xml" };
 
             // Act
@@ -603,7 +602,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         {
             // Arrange
             var type1 = typeof(ApiExplorerWebSite.Product).FullName;
-            var type2 = typeof(ModelStateDictionary).FullName;
+            var type2 = typeof(SerializableError).FullName;
             var expectedMediaTypes = new[] { "text/xml" };
 
             // Act
@@ -635,7 +634,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         {
             // Arrange
             var type1 = typeof(ApiExplorerWebSite.Product).FullName;
-            var type2 = typeof(ModelStateDictionary).FullName;
+            var type2 = typeof(SerializableError).FullName;
             var expectedMediaTypes = new[] { "application/json", "text/json", "application/xml", "text/xml" };
 
             // Act
@@ -667,7 +666,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         {
             // Arrange
             var type1 = typeof(ApiExplorerWebSite.Product).FullName;
-            var type2 = typeof(ModelStateDictionary).FullName;
+            var type2 = typeof(SerializableError).FullName;
             var expectedMediaTypes = new[] { "text/xml" };
 
             // Act

test/WebSites/ApiExplorerWebSite/Controllers/ApiExplorerResponseTypeWithAttributeController.cs

@@ -3,7 +3,6 @@
 
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Mvc;
-using Microsoft.AspNetCore.Mvc.ModelBinding;
 
 namespace ApiExplorerWebSite
 {
@@ -58,7 +57,7 @@ namespace ApiExplorerWebSite
         }
 
         [ProducesResponseType(typeof(Product), 201)]
-        [ProducesResponseType(typeof(ModelStateDictionary), 400)]
+        [ProducesResponseType(typeof(SerializableError), 400)]
         public Product CreateProductWithDefaultResponseContentTypes(Product product)
         {
             return null;
@@ -66,21 +65,21 @@ namespace ApiExplorerWebSite
 
         [Produces("text/xml")] // Has status code as 200 but is not applied as it does not set 'Type'
         [ProducesResponseType(typeof(Product), 201)]
-        [ProducesResponseType(typeof(ModelStateDictionary), 400)]
+        [ProducesResponseType(typeof(SerializableError), 400)]
         public Product CreateProductWithLimitedResponseContentTypes(Product product)
         {
             return null;
         }
 
         [ProducesResponseType(typeof(Product), 200)]
-        [ProducesResponseType(typeof(ModelStateDictionary), 400)]
+        [ProducesResponseType(typeof(SerializableError), 400)]
         public Product UpdateProductWithDefaultResponseContentTypes(Product product)
         {
             return null;
         }
 
         [Produces("text/xml", Type = typeof(Product))] // Has status code as 200
-        [ProducesResponseType(typeof(ModelStateDictionary), 400)]
+        [ProducesResponseType(typeof(SerializableError), 400)]
         public Product UpdateProductWithLimitedResponseContentTypes(Product product)
         {
             return null;