Polish ProblemDetails

* Add ability to set extended members on ProblemDetails
* Skip empty valued properties when serializing ProblemDetails

Fixes #8296
Fixes #8317

src/Microsoft.AspNetCore.Mvc.Core/ProblemDetails.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using Newtonsoft.Json;
 
 namespace Microsoft.AspNetCore.Mvc
 {
@@ -17,28 +18,47 @@ namespace Microsoft.AspNetCore.Mvc
         /// (e.g., using HTML [W3C.REC-html5-20141028]).  When this member is not present, its value is assumed to be
         /// "about:blank".
         /// </summary>
+        [JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
         public string Type { get; set; }
 
         /// <summary>
-        /// A short, human-readable summary of the problem type. It SHOULD NOT change from occurrence to occurrence
+        /// A short, human-readable summary of the problem type.It SHOULD NOT change from occurrence to occurrence
         /// of the problem, except for purposes of localization(e.g., using proactive content negotiation;
         /// see[RFC7231], Section 3.4).
         /// </summary>
+        [JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
         public string Title { get; set; }
 
         /// <summary>
         /// The HTTP status code([RFC7231], Section 6) generated by the origin server for this occurrence of the problem.
         /// </summary>
+        [JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
         public int? Status { get; set; }
 
         /// <summary>
         /// A human-readable explanation specific to this occurrence of the problem.
         /// </summary>
+        [JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
         public string Detail { get; set; }
 
         /// <summary>
-        /// A URI reference that identifies the specific occurrence of the problem. It may or may not yield further information if dereferenced.
+        /// A URI reference that identifies the specific occurrence of the problem.It may or may not yield further information if dereferenced.
         /// </summary>
+        [JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
         public string Instance { get; set; }
+
+        /// <summary>
+        /// Gets the <see cref="IDictionary{TKey, TValue}"/> for extension members.
+        /// <para>
+        /// Problem type definitions MAY extend the problem details object with additional members. Extension members appear in the same namespace as
+        /// other members of a problem type.
+        /// </para>
+        /// </summary>
+        /// <remarks>
+        /// The round-tripping behavior for <see cref="Extensions"/> is determined by the implementation of the Input \ Output formatters.
+        /// In particular, complex types or collection types may not round-trip to the original type when using the built-in JSON or XML formatters.
+        /// </remarks>
+        [JsonExtensionData]
+        public IDictionary<string, object> Extensions { get; } = new Dictionary<string, object>(StringComparer.Ordinal);
     }
 }

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

@@ -0,0 +1,187 @@
+// 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;
+using System.Globalization;
+using System.Xml;
+using System.Xml.Schema;
+using System.Xml.Serialization;
+
+namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
+{
+    /// <summary>
+    /// Wrapper class for <see cref="Mvc.ProblemDetails"/> to enable it to be serialized by the xml formatters.
+    /// </summary>
+    [XmlRoot(nameof(ProblemDetails))]
+    public class ProblemDetailsWrapper : IXmlSerializable, IUnwrappable
+    {
+        /// <summary>
+        /// Key used to represent dictionary elements with empty keys
+        /// </summary>
+        protected static readonly string EmptyKey = SerializableErrorWrapper.EmptyKey;
+
+        /// <summary>
+        /// Initializes a new instance of <see cref="ProblemDetailsWrapper"/>.
+        /// </summary>
+        public ProblemDetailsWrapper()
+            : this(new ProblemDetails())
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of <see cref="ProblemDetailsWrapper"/>.
+        /// </summary>
+        public ProblemDetailsWrapper(ProblemDetails problemDetails)
+        {
+            ProblemDetails = problemDetails;
+        }
+
+        internal ProblemDetails ProblemDetails { get; }
+
+        /// <inheritdoc />
+        public XmlSchema GetSchema() => null;
+
+        /// <inheritdoc />
+        public virtual void ReadXml(XmlReader reader)
+        {
+            if (reader == null)
+            {
+                throw new ArgumentNullException(nameof(reader));
+            }
+
+            if (reader.IsEmptyElement)
+            {
+                reader.Read();
+                return;
+            }
+
+            reader.ReadStartElement();
+            while (reader.NodeType != XmlNodeType.EndElement)
+            {
+                var key = XmlConvert.DecodeName(reader.LocalName);
+                ReadValue(reader, key);
+
+                reader.MoveToContent();
+            }
+
+            reader.ReadEndElement();
+        }
+
+        /// <summary>
+        /// Reads the value for the specified <paramref name="name"/> from the <paramref name="reader"/>.
+        /// </summary>
+        /// <param name="reader">The <see cref="XmlReader"/>.</param>
+        /// <param name="name">The name of the node.</param>
+        protected virtual void ReadValue(XmlReader reader, string name)
+        {
+            if (reader == null)
+            {
+                throw new ArgumentNullException(nameof(reader));
+            }
+
+            var value = reader.ReadInnerXml();
+
+            switch (name)
+            {
+                case nameof(ProblemDetails.Detail):
+                    ProblemDetails.Detail = value;
+                    break;
+
+                case nameof(ProblemDetails.Instance):
+                    ProblemDetails.Instance = value;
+                    break;
+
+                case nameof(ProblemDetails.Status):
+                    ProblemDetails.Status = string.IsNullOrEmpty(value) ?
+                        (int?)null :
+                        int.Parse(value, CultureInfo.InvariantCulture);
+                    break;
+
+                case nameof(ProblemDetails.Title):
+                    ProblemDetails.Title = value;
+                    break;
+
+                case nameof(ProblemDetails.Type):
+                    ProblemDetails.Type = value;
+                    break;
+
+                default:
+                    if (string.Equals(name, EmptyKey, StringComparison.Ordinal))
+                    {
+                        name = string.Empty;
+                    }
+
+                    ProblemDetails.Extensions.Add(name, value);
+                    break;
+            }
+        }
+
+        /// <inheritdoc />
+        public virtual void WriteXml(XmlWriter writer)
+        {
+            if (!string.IsNullOrEmpty(ProblemDetails.Detail))
+            {
+                writer.WriteElementString(
+                    XmlConvert.EncodeLocalName(nameof(ProblemDetails.Detail)),
+                    ProblemDetails.Detail);
+            }
+
+            if (!string.IsNullOrEmpty(ProblemDetails.Instance))
+            {
+                writer.WriteElementString(
+                    XmlConvert.EncodeLocalName(nameof(ProblemDetails.Instance)),
+                    ProblemDetails.Instance);
+            }
+
+            if (ProblemDetails.Status.HasValue)
+            {
+                writer.WriteStartElement(XmlConvert.EncodeLocalName(nameof(ProblemDetails.Status)));
+                writer.WriteValue(ProblemDetails.Status.Value);
+                writer.WriteEndElement();
+            }
+
+            if (!string.IsNullOrEmpty(ProblemDetails.Title))
+            {
+                writer.WriteElementString(
+                    XmlConvert.EncodeLocalName(nameof(ProblemDetails.Title)),
+                    ProblemDetails.Title);
+            }
+
+            if (!string.IsNullOrEmpty(ProblemDetails.Type))
+            {
+                writer.WriteElementString(
+                    XmlConvert.EncodeLocalName(nameof(ProblemDetails.Type)),
+                    ProblemDetails.Type);
+            }
+
+            foreach (var keyValuePair in ProblemDetails.Extensions)
+            {
+                var key = keyValuePair.Key;
+                var value = keyValuePair.Value;
+
+                if (string.IsNullOrEmpty(key))
+                {
+                    key = EmptyKey;
+                }
+
+                writer.WriteStartElement(XmlConvert.EncodeLocalName(key));
+                if (value != null)
+                {
+                    writer.WriteValue(value);
+                }
+
+                writer.WriteEndElement();
+            }
+        }
+
+        object IUnwrappable.Unwrap(Type declaredType)
+        {
+            if (declaredType == null)
+            {
+                throw new ArgumentNullException(nameof(declaredType));
+            }
+
+            return ProblemDetails;
+        }
+    }
+}

src/Microsoft.AspNetCore.Mvc.Formatters.Xml/Properties/AssemblyInfo.cs

@@ -0,0 +1,6 @@
+// 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.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("Microsoft.AspNetCore.Mvc.Formatters.Xml.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]

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

@@ -16,7 +16,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
     {
         // Element name used when ModelStateEntry's Key is empty. Dash in element name should avoid collisions with
         // other ModelState entries because the character is not legal in an expression name.
-        private static readonly string EmptyKey = "MVC-Empty";
+        internal static readonly string EmptyKey = "MVC-Empty";
 
         // Note: XmlSerializer requires to have default constructor
         public SerializableErrorWrapper()

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

@@ -0,0 +1,126 @@
+// 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;
+using System.Xml;
+using System.Xml.Serialization;
+
+namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
+{
+    /// <summary>
+    /// Wrapper class for <see cref="ValidationProblemDetails"/> to enable it to be serialized by the xml formatters.
+    /// </summary>
+    [XmlRoot(nameof(ValidationProblemDetails))]
+    public class ValidationProblemDetailsWrapper : ProblemDetailsWrapper, IUnwrappable
+    {
+        private static readonly string ErrorKey = "MVC-Errors";
+
+        /// <summary>
+        /// Initializes a new instance of <see cref="ValidationProblemDetailsWrapper"/>.
+        /// </summary>
+        public ValidationProblemDetailsWrapper()
+            : this(new ValidationProblemDetails())
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of <see cref="ValidationProblemDetailsWrapper"/> for the specified
+        /// <paramref name="problemDetails"/>.
+        /// </summary>
+        /// <param name="problemDetails">The <see cref="ProblemDetails"/>.</param>
+        public ValidationProblemDetailsWrapper(ValidationProblemDetails problemDetails)
+            : base(problemDetails)
+        {
+            ProblemDetails = problemDetails;
+        }
+
+        internal new ValidationProblemDetails ProblemDetails { get; }
+
+        /// <inheritdoc />
+        protected override void ReadValue(XmlReader reader, string name)
+        {
+            if (reader == null)
+            {
+                throw new ArgumentNullException(nameof(reader));
+            }
+
+            if (string.Equals(name, ErrorKey, StringComparison.Ordinal))
+            {
+                reader.Read();
+                ReadErrorProperty(reader);
+            }
+            else
+            {
+                base.ReadValue(reader, name);
+            }
+        }
+
+        private void ReadErrorProperty(XmlReader reader)
+        {
+            if (reader.IsEmptyElement)
+            {
+                return;
+            }
+
+            while (reader.NodeType != XmlNodeType.EndElement)
+            {
+                var key = XmlConvert.DecodeName(reader.LocalName);
+                var value = reader.ReadInnerXml();
+                if (string.Equals(EmptyKey, key, StringComparison.Ordinal))
+                {
+                    key = string.Empty;
+                }
+
+                ProblemDetails.Errors.Add(key, new[] { value });
+                reader.MoveToContent();
+            }
+        }
+
+        /// <inheritdoc />
+        public override void WriteXml(XmlWriter writer)
+        {
+            if (writer == null)
+            {
+                throw new ArgumentNullException(nameof(writer));
+            }
+
+            base.WriteXml(writer);
+
+            if (ProblemDetails.Errors.Count == 0)
+            {
+                return;
+            }
+
+            writer.WriteStartElement(XmlConvert.EncodeLocalName(ErrorKey));
+
+            foreach (var keyValuePair in ProblemDetails.Errors)
+            {
+                var key = keyValuePair.Key;
+                var value = keyValuePair.Value;
+                if (string.IsNullOrEmpty(key))
+                {
+                    key = EmptyKey;
+                }
+
+                writer.WriteStartElement(XmlConvert.EncodeLocalName(key));
+                if (value != null)
+                {
+                    writer.WriteValue(value);
+                }
+
+                writer.WriteEndElement();
+            }
+            writer.WriteEndElement();
+        }
+
+        object IUnwrappable.Unwrap(Type declaredType)
+        {
+            if (declaredType == null)
+            {
+                throw new ArgumentNullException(nameof(declaredType));
+            }
+
+            return ProblemDetails;
+        }
+    }
+}

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

@@ -44,5 +44,24 @@ namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
 
             return null;
         }
+
+        internal static IList<IWrapperProviderFactory> GetDefaultProviderFactories()
+        {
+            var wrapperProviderFactories = new List<IWrapperProviderFactory>();
+
+            wrapperProviderFactories.Add(new SerializableErrorWrapperProviderFactory());
+
+            wrapperProviderFactories.Add(new WrapperProviderFactory(
+                typeof(ProblemDetails),
+                typeof(ProblemDetailsWrapper),
+                value => new ProblemDetailsWrapper((ProblemDetails)value)));
+
+            wrapperProviderFactories.Add(new WrapperProviderFactory(
+                typeof(ValidationProblemDetails),
+                typeof(ValidationProblemDetailsWrapper),
+                value => new ValidationProblemDetailsWrapper((ValidationProblemDetails)value)));
+
+            return wrapperProviderFactories;
+        }
     }
 }

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

@@ -0,0 +1,50 @@
+// 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;
+
+namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
+{
+    internal class WrapperProviderFactory : IWrapperProviderFactory
+    {
+        public WrapperProviderFactory(Type declaredType, Type wrappingType, Func<object, object> wrapper)
+        {
+            DeclaredType = declaredType;
+            WrappingType = wrappingType;
+            Wrapper = wrapper;
+        }
+
+        public Type DeclaredType { get; }
+
+        public Type WrappingType { get; }
+
+        public Func<object, object> Wrapper { get; }
+
+        public IWrapperProvider GetProvider(WrapperProviderContext context)
+        {
+            if (context.DeclaredType == DeclaredType)
+            {
+                return new WrapperProvider(this);
+            }
+
+            return null;
+        }
+
+        private class WrapperProvider : IWrapperProvider
+        {
+            private readonly WrapperProviderFactory _wrapperFactory;
+
+            public WrapperProvider(WrapperProviderFactory wrapperFactory)
+            {
+                _wrapperFactory = wrapperFactory;
+            }
+
+            public Type WrappingType => _wrapperFactory.WrappingType;
+
+            public object Wrap(object original)
+            {
+                return _wrapperFactory.Wrapper(original);
+            }
+        }
+    }
+}

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

@@ -46,8 +46,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters
 
             _serializerSettings = new DataContractSerializerSettings();
 
-            WrapperProviderFactories = new List<IWrapperProviderFactory>();
-            WrapperProviderFactories.Add(new SerializableErrorWrapperProviderFactory());
+            WrapperProviderFactories = WrapperProviderFactoriesExtensions.GetDefaultProviderFactories();
         }
 
         /// <summary>

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

@@ -76,9 +76,8 @@ namespace Microsoft.AspNetCore.Mvc.Formatters
 
             _serializerSettings = new DataContractSerializerSettings();
 
-            WrapperProviderFactories = new List<IWrapperProviderFactory>();
+            WrapperProviderFactories = WrapperProviderFactoriesExtensions.GetDefaultProviderFactories();
             WrapperProviderFactories.Add(new EnumerableWrapperProviderFactory(WrapperProviderFactories));
-            WrapperProviderFactories.Add(new SerializableErrorWrapperProviderFactory());
 
             _logger = loggerFactory?.CreateLogger(GetType());
         }

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

@@ -43,8 +43,7 @@ namespace Microsoft.AspNetCore.Mvc.Formatters
             SupportedMediaTypes.Add(MediaTypeHeaderValues.TextXml);
             SupportedMediaTypes.Add(MediaTypeHeaderValues.ApplicationAnyXmlSyntax);
 
-            WrapperProviderFactories = new List<IWrapperProviderFactory>();
-            WrapperProviderFactories.Add(new SerializableErrorWrapperProviderFactory());
+            WrapperProviderFactories = WrapperProviderFactoriesExtensions.GetDefaultProviderFactories();
         }
 
         /// <summary>

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

@@ -73,9 +73,8 @@ namespace Microsoft.AspNetCore.Mvc.Formatters
 
             WriterSettings = writerSettings;
 
-            WrapperProviderFactories = new List<IWrapperProviderFactory>();
+            WrapperProviderFactories = WrapperProviderFactoriesExtensions.GetDefaultProviderFactories();
             WrapperProviderFactories.Add(new EnumerableWrapperProviderFactory(WrapperProviderFactories));
-            WrapperProviderFactories.Add(new SerializableErrorWrapperProviderFactory());
 
             _logger = loggerFactory?.CreateLogger(GetType());
         }

test/Microsoft.AspNetCore.Mvc.Formatters.Xml.Test/ProblemDetailsWrapperTest.cs

@@ -0,0 +1,100 @@
+// 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.IO;
+using System.Linq;
+using System.Runtime.Serialization;
+using System.Text;
+using System.Xml;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
+{
+    public class ProblemDetailsWrapperTest
+    {
+        [Fact]
+        public void ReadXml_ReadsProblemDetailsXml()
+        {
+            // Arrange
+            var xml = "<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
+                "<ProblemDetails>" +
+                "<Title>Some title</Title>" +
+                "<Status>403</Status>" +
+                "<Instance>Some instance</Instance>" +
+                "<key1>Test Value 1</key1>" +
+                "<_x005B_key2_x005D_>Test Value 2</_x005B_key2_x005D_>" +
+                "<MVC-Empty>Test Value 3</MVC-Empty>" +
+                "</ProblemDetails>";
+            var serializer = new DataContractSerializer(typeof(ProblemDetailsWrapper));
+
+            // Act
+            var value = serializer.ReadObject(
+                new MemoryStream(Encoding.UTF8.GetBytes(xml)));
+
+            // Assert
+            var problemDetails = Assert.IsType<ProblemDetailsWrapper>(value).ProblemDetails;
+            Assert.Equal("Some title", problemDetails.Title);
+            Assert.Equal("Some instance", problemDetails.Instance);
+            Assert.Equal(403, problemDetails.Status);
+
+            Assert.Collection(
+                problemDetails.Extensions.OrderBy(kvp => kvp.Key),
+                kvp =>
+                {
+                    Assert.Empty(kvp.Key);
+                    Assert.Equal("Test Value 3", kvp.Value);
+                },
+                kvp =>
+                {
+                    Assert.Equal("[key2]", kvp.Key);
+                    Assert.Equal("Test Value 2", kvp.Value);
+                },
+                kvp =>
+                {
+                    Assert.Equal("key1", kvp.Key);
+                    Assert.Equal("Test Value 1", kvp.Value);
+                });
+        }
+
+
+        [Fact]
+        public void WriteXml_WritesValidXml()
+        {
+            // Arrange
+            var problemDetails = new ProblemDetails
+            {
+                Title = "Some title",
+                Detail = "Some detail",
+                Extensions =
+                {
+                    ["key1"] = "Test Value 1",
+                    ["[Key2]"] = "Test Value 2",
+                    [""] = "Test Value 3",
+                },
+            };
+
+            var wrapper = new ProblemDetailsWrapper(problemDetails);
+            var outputStream = new MemoryStream();
+            var expectedContent = "<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
+                "<ProblemDetails>" +
+                "<Detail>Some detail</Detail>" +
+                "<Title>Some title</Title>" +
+                "<key1>Test Value 1</key1>" +
+                "<_x005B_Key2_x005D_>Test Value 2</_x005B_Key2_x005D_>" +
+                "<MVC-Empty>Test Value 3</MVC-Empty>" +
+                "</ProblemDetails>";
+
+            // Act
+            using (var xmlWriter = XmlWriter.Create(outputStream))
+            {
+                var dataContractSerializer = new DataContractSerializer(wrapper.GetType());
+                dataContractSerializer.WriteObject(xmlWriter, wrapper);
+            }
+            outputStream.Position = 0;
+            var res = new StreamReader(outputStream, Encoding.UTF8).ReadToEnd();
+
+            // Assert
+            Assert.Equal(expectedContent, res);
+        }
+    }
+}

test/Microsoft.AspNetCore.Mvc.Formatters.Xml.Test/ValidationProblemDetailsWrapperTest.cs

@@ -0,0 +1,226 @@
+// 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.IO;
+using System.Linq;
+using System.Runtime.Serialization;
+using System.Text;
+using System.Xml;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
+{
+    public class ValidationProblemDetailsWrapperTest
+    {
+        [Fact]
+        public void ReadXml_ReadsValidationProblemDetailsXml()
+        {
+            // Arrange
+            var xml = "<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
+                "<ValidationProblemDetails>" +
+                "<Title>Some title</Title>" +
+                "<Status>400</Status>" +
+                "<Instance>Some instance</Instance>" +
+                "<key1>Test Value 1</key1>" +
+                "<_x005B_key2_x005D_>Test Value 2</_x005B_key2_x005D_>" +
+                "<MVC-Errors>" +
+                "<error1>Test error 1 Test error 2</error1>" +
+                "<_x005B_error2_x005D_>Test error 3</_x005B_error2_x005D_>" +
+                "<MVC-Empty>Test error 4</MVC-Empty>" +
+                "</MVC-Errors>" +
+                "</ValidationProblemDetails>";
+            var serializer = new DataContractSerializer(typeof(ValidationProblemDetailsWrapper));
+
+            // Act
+            var value = serializer.ReadObject(
+                new MemoryStream(Encoding.UTF8.GetBytes(xml)));
+
+            // Assert
+            var problemDetails = Assert.IsType<ValidationProblemDetailsWrapper>(value).ProblemDetails;
+            Assert.Equal("Some title", problemDetails.Title);
+            Assert.Equal("Some instance", problemDetails.Instance);
+            Assert.Equal(400, problemDetails.Status);
+
+            Assert.Collection(
+                problemDetails.Extensions.OrderBy(kvp => kvp.Key),
+                kvp =>
+                {
+                    Assert.Equal("[key2]", kvp.Key);
+                    Assert.Equal("Test Value 2", kvp.Value);
+                },
+                kvp =>
+                {
+                    Assert.Equal("key1", kvp.Key);
+                    Assert.Equal("Test Value 1", kvp.Value);
+                });
+
+            Assert.Collection(
+                problemDetails.Errors.OrderBy(kvp => kvp.Key),
+                kvp =>
+                {
+                    Assert.Empty(kvp.Key);
+                    Assert.Equal(new[] { "Test error 4" }, kvp.Value);
+                },
+                kvp =>
+                {
+                    Assert.Equal("[error2]", kvp.Key);
+                    Assert.Equal(new[] { "Test error 3" }, kvp.Value);
+                },
+                kvp =>
+                {
+                    Assert.Equal("error1", kvp.Key);
+                    Assert.Equal(new[] { "Test error 1 Test error 2" }, kvp.Value);
+                });
+        }
+
+        [Fact]
+        public void ReadXml_ReadsValidationProblemDetailsXml_WithNoErrors()
+        {
+            // Arrange
+            var xml = "<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
+                "<ValidationProblemDetails>" +
+                "<Title>Some title</Title>" +
+                "<Status>400</Status>" +
+                "<Instance>Some instance</Instance>" +
+                "<key1>Test Value 1</key1>" +
+                "<_x005B_key2_x005D_>Test Value 2</_x005B_key2_x005D_>" +
+                "</ValidationProblemDetails>";
+            var serializer = new DataContractSerializer(typeof(ValidationProblemDetailsWrapper));
+
+            // Act
+            var value = serializer.ReadObject(
+                new MemoryStream(Encoding.UTF8.GetBytes(xml)));
+
+            // Assert
+            var problemDetails = Assert.IsType<ValidationProblemDetailsWrapper>(value).ProblemDetails;
+            Assert.Equal("Some title", problemDetails.Title);
+            Assert.Equal("Some instance", problemDetails.Instance);
+            Assert.Equal(400, problemDetails.Status);
+
+            Assert.Collection(
+                problemDetails.Extensions,
+                kvp =>
+                {
+                    Assert.Equal("key1", kvp.Key);
+                    Assert.Equal("Test Value 1", kvp.Value);
+                },
+                kvp =>
+                {
+                    Assert.Equal("[key2]", kvp.Key);
+                    Assert.Equal("Test Value 2", kvp.Value);
+                });
+
+            Assert.Empty(problemDetails.Errors);
+        }
+
+        [Fact]
+        public void ReadXml_ReadsValidationProblemDetailsXml_WithEmptyErrorsElement()
+        {
+            // Arrange
+            var xml = "<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
+                "<ValidationProblemDetails>" +
+                "<Title>Some title</Title>" +
+                "<Status>400</Status>" +
+                "<MVC-Errors />" +
+                "</ValidationProblemDetails>";
+            var serializer = new DataContractSerializer(typeof(ValidationProblemDetailsWrapper));
+
+            // Act
+            var value = serializer.ReadObject(
+                new MemoryStream(Encoding.UTF8.GetBytes(xml)));
+
+            // Assert
+            var problemDetails = Assert.IsType<ValidationProblemDetailsWrapper>(value).ProblemDetails;
+            Assert.Equal("Some title", problemDetails.Title);
+            Assert.Equal(400, problemDetails.Status);
+            Assert.Empty(problemDetails.Errors);
+        }
+
+        [Fact]
+        public void WriteXml_WritesValidXml()
+        {
+            // Arrange
+            var problemDetails = new ValidationProblemDetails
+            {
+                Title = "Some title",
+                Detail = "Some detail",
+                Extensions =
+                {
+                    ["key1"] = "Test Value 1",
+                    ["[Key2]"] = "Test Value 2"
+                },
+                Errors =
+                {
+                    { "error1", new[] {"Test error 1", "Test error 2" } },
+                    { "[error2]", new[] {"Test error 3" } },
+                    { "", new[] { "Test error 4" } },
+                }
+            };
+
+            var wrapper = new ValidationProblemDetailsWrapper(problemDetails);
+            var outputStream = new MemoryStream();
+            var expectedContent = "<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
+                "<ValidationProblemDetails>" +
+                "<Detail>Some detail</Detail>" +
+                "<Title>Some title</Title>" +
+                "<key1>Test Value 1</key1>" +
+                "<_x005B_Key2_x005D_>Test Value 2</_x005B_Key2_x005D_>" +
+                "<MVC-Errors>" +
+                "<error1>Test error 1 Test error 2</error1>" +
+                "<_x005B_error2_x005D_>Test error 3</_x005B_error2_x005D_>" +
+                "<MVC-Empty>Test error 4</MVC-Empty>" +
+                "</MVC-Errors>" +
+                "</ValidationProblemDetails>";
+
+            // Act
+            using (var xmlWriter = XmlWriter.Create(outputStream))
+            {
+                var dataContractSerializer = new DataContractSerializer(wrapper.GetType());
+                dataContractSerializer.WriteObject(xmlWriter, wrapper);
+            }
+            outputStream.Position = 0;
+            var res = new StreamReader(outputStream, Encoding.UTF8).ReadToEnd();
+
+            // Assert
+            Assert.Equal(expectedContent, res);
+        }
+
+        [Fact]
+        public void WriteXml_WithNoValidationErrors()
+        {
+            // Arrange
+            var problemDetails = new ValidationProblemDetails
+            {
+                Title = "Some title",
+                Detail = "Some detail",
+                Extensions =
+                {
+                    ["key1"] = "Test Value 1",
+                    ["[Key2]"] = "Test Value 2"
+                },
+            };
+
+            var wrapper = new ValidationProblemDetailsWrapper(problemDetails);
+            var outputStream = new MemoryStream();
+            var expectedContent = "<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
+                "<ValidationProblemDetails>" +
+                "<Detail>Some detail</Detail>" +
+                "<Title>Some title</Title>" +
+                "<key1>Test Value 1</key1>" +
+                "<_x005B_Key2_x005D_>Test Value 2</_x005B_Key2_x005D_>" +
+                "</ValidationProblemDetails>";
+
+            // Act
+            using (var xmlWriter = XmlWriter.Create(outputStream))
+            {
+                var dataContractSerializer = new DataContractSerializer(wrapper.GetType());
+                dataContractSerializer.WriteObject(xmlWriter, wrapper);
+            }
+            outputStream.Position = 0;
+            var res = new StreamReader(outputStream, Encoding.UTF8).ReadToEnd();
+
+            // Assert
+            Assert.Equal(expectedContent, res);
+        }
+    }
+}

test/Microsoft.AspNetCore.Mvc.Formatters.Xml.Test/WrapperProviderFactoryExtensionsTest.cs

@@ -0,0 +1,34 @@
+// 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 Xunit;
+
+namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
+{
+    public class WrapperProviderFactoryExtensionsTest
+    {
+        [Fact]
+        public void GetDefaultProviderFactories_GetsFactoriesUsedByInputAndOutputFormatters()
+        {
+            // Act
+            var factoryProviders = WrapperProviderFactoriesExtensions.GetDefaultProviderFactories();
+
+            // Assert
+            Assert.Collection(
+                factoryProviders,
+                factory => Assert.IsType<SerializableErrorWrapperProviderFactory>(factory),
+                factory =>
+                {
+                    var wrapperProviderFactory = Assert.IsType<WrapperProviderFactory>(factory);
+                    Assert.Equal(typeof(ProblemDetails), wrapperProviderFactory.DeclaredType);
+                    Assert.Equal(typeof(ProblemDetailsWrapper), wrapperProviderFactory.WrappingType);
+                },
+                factory =>
+                {
+                    var wrapperProviderFactory = Assert.IsType<WrapperProviderFactory>(factory);
+                    Assert.Equal(typeof(ValidationProblemDetails), wrapperProviderFactory.DeclaredType);
+                    Assert.Equal(typeof(ValidationProblemDetailsWrapper), wrapperProviderFactory.WrappingType);
+                });
+        }
+    }
+}

test/Microsoft.AspNetCore.Mvc.Formatters.Xml.Test/WrapperProviderFactoryTest.cs

@@ -0,0 +1,63 @@
+// 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 Xunit;
+
+namespace Microsoft.AspNetCore.Mvc.Formatters.Xml
+{
+    public class WrapperProviderFactoryTest
+    {
+        [Fact]
+        public void GetProvider_ReturnsNull_IfTypeDoesNotMatch()
+        {
+            // Arrange
+            var provider = new WrapperProviderFactory(
+                typeof(ProblemDetails),
+                typeof(ProblemDetailsWrapper),
+                _ => null);
+            var context = new WrapperProviderContext(typeof(SerializableError), isSerialization: true);
+
+            // Act
+            var result = provider.GetProvider(context);
+
+            // Assert
+            Assert.Null(result);
+        }
+
+        [Fact]
+        public void GetProvider_ReturnsNull_IfTypeIsSubtype()
+        {
+            // Arrange
+            var provider = new WrapperProviderFactory(
+                typeof(ProblemDetails),
+                typeof(ProblemDetailsWrapper),
+                _ => null);
+            var context = new WrapperProviderContext(typeof(ValidationProblemDetails), isSerialization: true);
+
+            // Act
+            var result = provider.GetProvider(context);
+
+            // Assert
+            Assert.Null(result);
+        }
+
+        [Fact]
+        public void GetProvider_ReturnsValue_IfTypeMatches()
+        {
+            // Arrange
+            var expected = new object();
+            var providerFactory = new WrapperProviderFactory(
+                typeof(ProblemDetails),
+                typeof(ProblemDetailsWrapper),
+                _ => expected);
+            var context = new WrapperProviderContext(typeof(ProblemDetails), isSerialization: true);
+
+            // Act
+            var provider = providerFactory.GetProvider(context);
+            var result = provider.Wrap(new ProblemDetails());
+
+            // Assert
+            Assert.Same(expected, result);
+        }
+    }
+}

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

@@ -10,6 +10,7 @@ using System.Threading.Tasks;
 using BasicWebSite.Models;
 using Microsoft.AspNetCore.Hosting;
 using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Mvc.FunctionalTests
@@ -116,8 +117,8 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
             };
             var expected = new Dictionary<string, string[]>
             {
-                {"Name", new string[] {"The field Name must be a string with a minimum length of 5 and a maximum length of 30."}},
-                {"Zip", new string[]{ @"The field Zip must match the regular expression '\d{5}'."}}
+                {"Name", new[] {"The field Name must be a string with a minimum length of 5 and a maximum length of 30."}},
+                {"Zip", new[] { @"The field Zip must match the regular expression '\d{5}'."}}
             };
             var contactString = JsonConvert.SerializeObject(contactModel);
 
@@ -261,5 +262,62 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
             var problemDetails = JsonConvert.DeserializeObject<ProblemDetails>(content);
             Assert.Equal(404, problemDetails.Status);
         }
+
+        [Fact]
+        public async Task SerializingProblemDetails_IgnoresNullValuedProperties()
+        {
+            // Arrange
+            var expected = new[] { "status", "title", "type" };
+
+            // Act
+            var response = await Client.GetAsync("/contact/ActionReturningStatusCodeResult");
+
+            // Assert
+            await response.AssertStatusCodeAsync(HttpStatusCode.NotFound);
+            var content = await response.Content.ReadAsStringAsync();
+
+            // Verify that null-valued properties on ProblemDetails are not serialized.
+            var json = JObject.Parse(content);
+            Assert.Equal(expected, json.Properties().OrderBy(p => p.Name).Select(p => p.Name));
+        }
+
+        [Fact]
+        public async Task SerializingProblemDetails_WithAllValuesSpecified()
+        {
+            // Arrange
+            var expected = new[] { "detail", "instance", "status", "title", "tracking-id", "type" };
+
+            // Act
+            var response = await Client.GetAsync("/contact/ActionReturningProblemDetails");
+
+            // Assert
+            await response.AssertStatusCodeAsync(HttpStatusCode.NotFound);
+            var content = await response.Content.ReadAsStringAsync();
+            var json = JObject.Parse(content);
+            Assert.Equal(expected, json.Properties().OrderBy(p => p.Name).Select(p => p.Name));
+        }
+
+        [Fact]
+        public async Task SerializingValidationProblemDetails_WithExtensionData()
+        {
+            // Act
+            var response = await Client.GetAsync("/contact/ActionReturningValidationProblemDetails");
+
+            // Assert
+            await response.AssertStatusCodeAsync(HttpStatusCode.BadRequest);
+            var content = await response.Content.ReadAsStringAsync();
+            var validationProblemDetails = JsonConvert.DeserializeObject<ValidationProblemDetails>(content);
+
+            Assert.Equal("Error", validationProblemDetails.Title);
+            Assert.Equal(400, validationProblemDetails.Status);
+            Assert.Equal("27", validationProblemDetails.Extensions["tracking-id"]);
+            Assert.Collection(
+                validationProblemDetails.Errors,
+                kvp =>
+                {
+                    Assert.Equal("Error1", kvp.Key);
+                    Assert.Equal(new[] { "Error Message" }, kvp.Value);
+                });
+        }
     }
 }

test/Microsoft.AspNetCore.Mvc.FunctionalTests/Infrastructure/HttpClientExtensions.cs

@@ -53,7 +53,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
 
             throw new StatusCodeMismatchException
             {
-                ExpectedStatusCode = HttpStatusCode.OK,
+                ExpectedStatusCode = expectedStatusCode,
                 ActualStatusCode = response.StatusCode,
                 ResponseContent = responseContent,
             };
@@ -71,7 +71,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
             {
                 get
                 {
-                    return $"Excepted status code 200. Actual {ActualStatusCode}. Response Content:" + Environment.NewLine + ResponseContent;
+                    return $"Excepted status code {ExpectedStatusCode}. Actual {ActualStatusCode}. Response Content:" + Environment.NewLine + ResponseContent;
                 }
             }
         }

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

@@ -208,5 +208,68 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
                 "</ArrayOfSerializableErrorWrapper>",
                 result);
         }
+
+        [Fact]
+        public async Task ProblemDetails_IsSerialized()
+        {
+            // Arrange
+            var expected = @"<ProblemDetails><Status>404</Status><Title>Not Found</Title><Type>https://tools.ietf.org/html/rfc7231#section-6.5.4</Type></ProblemDetails>";
+
+            // Act
+            var response = await Client.GetAsync("/api/XmlDataContractApi/ActionReturningClientErrorStatusCodeResult");
+
+            // Assert
+            await response.AssertStatusCodeAsync(HttpStatusCode.NotFound);
+            var content = await response.Content.ReadAsStringAsync();
+            XmlAssert.Equal(expected, content);
+        }
+
+        [Fact]
+        public async Task ProblemDetails_WithExtensionMembers_IsSerialized()
+        {
+            // Arrange
+            var expected = @"<ProblemDetails><Instance>instance</Instance><Status>404</Status><Title>title</Title>
+<Correlation>correlation</Correlation><Accounts>Account1 Account2</Accounts></ProblemDetails>";
+
+            // Act
+            var response = await Client.GetAsync("/api/XmlDataContractApi/ActionReturningProblemDetails");
+
+            // Assert
+            await response.AssertStatusCodeAsync(HttpStatusCode.NotFound);
+            var content = await response.Content.ReadAsStringAsync();
+            XmlAssert.Equal(expected, content);
+        }
+
+        [Fact]
+        public async Task ValidationProblemDetails_IsSerialized()
+        {
+            // Arrange
+            var expected = @"<ValidationProblemDetails><Status>400</Status><Title>One or more validation errors occurred.</Title>
+<MVC-Errors><State>The State field is required.</State></MVC-Errors></ValidationProblemDetails>";
+
+            // Act
+            var response = await Client.GetAsync("/api/XmlDataContractApi/ActionReturningValidationProblem");
+
+            // Assert
+            await response.AssertStatusCodeAsync(HttpStatusCode.BadRequest);
+            var content = await response.Content.ReadAsStringAsync();
+            XmlAssert.Equal(expected, content);
+        }
+
+        [Fact]
+        public async Task ValidationProblemDetails_WithExtensionMembers_IsSerialized()
+        {
+            // Arrange
+            var expected = @"<ValidationProblemDetails><Detail>some detail</Detail><Status>400</Status><Title>One or more validation errors occurred.</Title>
+<Type>some type</Type><CorrelationId>correlation</CorrelationId><MVC-Errors><Error1>ErrorValue</Error1></MVC-Errors></ValidationProblemDetails>";
+
+            // Act
+            var response = await Client.GetAsync("/api/XmlDataContractApi/ActionReturningValidationDetailsWithMetadata");
+
+            // Assert
+            await response.AssertStatusCodeAsync(HttpStatusCode.BadRequest);
+            var content = await response.Content.ReadAsStringAsync();
+            XmlAssert.Equal(expected, content);
+        }
     }
-}
+}

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

@@ -183,5 +183,68 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
                 "<key4>key2-error</key4></SerializableErrorWrapper></ArrayOfSerializableErrorWrapper>",
                 result);
         }
+
+        [Fact]
+        public async Task ProblemDetails_IsSerialized()
+        {
+            // Arrange
+            var expected = @"<ProblemDetails><Status>404</Status><Title>Not Found</Title><Type>https://tools.ietf.org/html/rfc7231#section-6.5.4</Type></ProblemDetails>";
+
+            // Act
+            var response = await Client.GetAsync("/api/XmlSerializerApi/ActionReturningClientErrorStatusCodeResult");
+
+            // Assert
+            await response.AssertStatusCodeAsync(HttpStatusCode.NotFound);
+            var content = await response.Content.ReadAsStringAsync();
+            XmlAssert.Equal(expected, content);
+        }
+
+        [Fact]
+        public async Task ProblemDetails_WithExtensionMembers_IsSerialized()
+        {
+            // Arrange
+            var expected = @"<ProblemDetails><Instance>instance</Instance><Status>404</Status><Title>title</Title>
+<Correlation>correlation</Correlation><Accounts>Account1 Account2</Accounts></ProblemDetails>";
+
+            // Act
+            var response = await Client.GetAsync("/api/XmlSerializerApi/ActionReturningProblemDetails");
+
+            // Assert
+            await response.AssertStatusCodeAsync(HttpStatusCode.NotFound);
+            var content = await response.Content.ReadAsStringAsync();
+            XmlAssert.Equal(expected, content);
+        }
+
+        [Fact]
+        public async Task ValidationProblemDetails_IsSerialized()
+        {
+            // Arrange
+            var expected = @"<ValidationProblemDetails><Status>400</Status><Title>One or more validation errors occurred.</Title>
+<MVC-Errors><State>The State field is required.</State></MVC-Errors></ValidationProblemDetails>";
+
+            // Act
+            var response = await Client.GetAsync("/api/XmlSerializerApi/ActionReturningValidationProblem");
+
+            // Assert
+            await response.AssertStatusCodeAsync(HttpStatusCode.BadRequest);
+            var content = await response.Content.ReadAsStringAsync();
+            XmlAssert.Equal(expected, content);
+        }
+
+        [Fact]
+        public async Task ValidationProblemDetails_WithExtensionMembers_IsSerialized()
+        {
+            // Arrange
+            var expected = @"<ValidationProblemDetails><Detail>some detail</Detail><Status>400</Status><Title>One or more validation errors occurred.</Title>
+<Type>some type</Type><CorrelationId>correlation</CorrelationId><MVC-Errors><Error1>ErrorValue</Error1></MVC-Errors></ValidationProblemDetails>";
+
+            // Act
+            var response = await Client.GetAsync("/api/XmlSerializerApi/ActionReturningValidationDetailsWithMetadata");
+
+            // Assert
+            await response.AssertStatusCodeAsync(HttpStatusCode.BadRequest);
+            var content = await response.Content.ReadAsStringAsync();
+            XmlAssert.Equal(expected, content);
+        }
     }
 }

test/WebSites/BasicWebSite/Controllers/ContactApiController.cs

@@ -91,6 +91,41 @@ namespace BasicWebSite
             return NotFound();
         }
 
+        [HttpGet("[action]")]
+        public ActionResult<int> ActionReturningProblemDetails()
+        {
+            return NotFound(new ProblemDetails
+            {
+                Title = "Not Found",
+                Type = "Type",
+                Detail = "Detail",
+                Status = 404,
+                Instance = "Instance",
+                Extensions =
+                {
+                    ["tracking-id"] = 27,
+                },
+            });
+        }
+
+        [HttpGet("[action]")]
+        public ActionResult<int> ActionReturningValidationProblemDetails()
+        {
+            return BadRequest(new ValidationProblemDetails
+            {
+                Title = "Error",
+                Status = 400,
+                Extensions =
+                {
+                    ["tracking-id"] = "27",
+                },
+                Errors =
+                {
+                    { "Error1", new[] { "Error Message" } },
+                },
+            });
+        }
+
         private class TestModelBinder : IModelBinder
         {
             public Task BindModelAsync(ModelBindingContext bindingContext)

test/WebSites/XmlFormattersWebSite/Controllers/XmlApiControllerBase.cs

@@ -0,0 +1,55 @@
+// 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;
+using Microsoft.AspNetCore.Mvc;
+using XmlFormattersWebSite.Models;
+
+namespace XmlFormattersWebSite
+{
+    [ApiController]
+    [Route("api/[controller]/[action]")]
+    public abstract class XmlApiControllerBase : ControllerBase
+    {
+        [HttpGet]
+        public ActionResult<Person> ActionReturningClientErrorStatusCodeResult()
+            => NotFound();
+
+        [HttpGet]
+        public ActionResult<Person> ActionReturningProblemDetails()
+        {
+            return NotFound(new ProblemDetails
+            {
+                Instance = "instance",
+                Title = "title",
+                Extensions =
+                {
+                    ["Correlation"] = "correlation",
+                    ["Accounts"] = new[] { "Account1", "Account2" },
+                },
+            });
+        }
+
+        [HttpGet]
+        public ActionResult<Person> ActionReturningValidationProblem([FromQuery] Address address)
+            => throw new NotImplementedException();
+
+        [HttpGet]
+        public ActionResult<Person> ActionReturningValidationDetailsWithMetadata()
+        {
+            return new BadRequestObjectResult(new ValidationProblemDetails
+            {
+                Detail = "some detail",
+                Type = "some type",
+                Extensions =
+                {
+                    ["CorrelationId"] = "correlation",
+                },
+                Errors =
+                {
+                    ["Error1"] = new[] { "ErrorValue"},
+                },
+            });
+        }
+    }
+}

test/WebSites/XmlFormattersWebSite/Controllers/XmlDataContractApiController.cs

@@ -0,0 +1,29 @@
+// 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 Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.Mvc.Filters;
+using Microsoft.AspNetCore.Mvc.Formatters;
+
+namespace XmlFormattersWebSite
+{
+    [SetupOutputFormatters]
+    public class XmlDataContractApiController : XmlApiControllerBase
+    {
+        private class SetupOutputFormattersAttribute : ResultFilterAttribute
+        {
+            public override void OnResultExecuting(ResultExecutingContext context)
+            {
+                if (!(context.Result is ObjectResult objectResult))
+                {
+                    return;
+                }
+
+                // Both kinds of Xml serializers are configured for this application and use custom content-types to do formatter
+                // selection. The globally configured formatters rely on custom content-type to perform conneg which does not play
+                // well the ProblemDetails returning filters that defaults to using application/xml. We'll explicitly select the formatter for this controller.
+                objectResult.Formatters.Add(new XmlDataContractSerializerOutputFormatter());
+            }
+        }
+    }
+}

test/WebSites/XmlFormattersWebSite/Controllers/XmlSerializedApiController.cs

@@ -0,0 +1,29 @@
+// 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 Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.Mvc.Filters;
+using Microsoft.AspNetCore.Mvc.Formatters;
+
+namespace XmlFormattersWebSite
+{
+    [SetupOutputFormatters]
+    public class XmlSerializerApiController : XmlApiControllerBase
+    {
+        private class SetupOutputFormattersAttribute : ResultFilterAttribute
+        {
+            public override void OnResultExecuting(ResultExecutingContext context)
+            {
+                if (!(context.Result is ObjectResult objectResult))
+                {
+                    return;
+                }
+
+                // Both kinds of Xml serializers are configured for this application and use custom content-types to do formatter
+                // selection. The globally configured formatters rely on custom content-type to perform conneg which does not play
+                // well the ProblemDetails returning filters that defaults to using application/xml. We'll explicitly select the formatter for this controller.
+                objectResult.Formatters.Add(new XmlSerializerOutputFormatter());
+            }
+        }
+    }
+}