Fix mtom message headers

Author: mconnew

src/System.ServiceModel.Http/src/System/ServiceModel/Channels/HttpChannelFactory.cs

@@ -5,6 +5,7 @@
 using System.Diagnostics.Contracts;
 using System.Globalization;
 using System.IdentityModel.Selectors;
+using System.Linq;
 using System.Net;
 using System.Net.Http;
 using System.Net.Http.Headers;
@@ -1030,6 +1031,15 @@ public async Task SendRequestAsync(Message message, TimeoutHelper timeoutHelper)
                         if (!suppressEntityBody)
                         {
                             httpRequestMessage.Content = MessageContent.Create(_factory, request, _timeoutHelper);
+                            var contentType = httpRequestMessage.Content.Headers.ContentType;
+                            if (contentType!= null &&
+                                contentType.MediaType == "multipart/related" &&
+                                contentType.Parameters.Contains(new NameValueHeaderValue("type", "\"application/xop+xml\"")))
+                            {
+                                // For MTOM messages, add a MIME version header
+                                AddMimeVersion("1.0");
+                            }
+
                         }
 
                         if (Fx.IsUap)
@@ -1095,6 +1105,11 @@ public async Task SendRequestAsync(Message message, TimeoutHelper timeoutHelper)
                     }
                 }
 
+                private void AddMimeVersion(string version)
+                {
+                    _httpRequestMessage.Headers.Add(HttpChannelUtilities.MIMEVersionHeader, version);
+                }
+
                 private void Cleanup()
                 {
                     s_cancelCts(_httpSendCts);

src/System.ServiceModel.Primitives/src/System/ServiceModel/Channels/MtomMessageEncoder.cs

@@ -423,12 +423,12 @@ public override Message ReadMessage(Stream stream, int maxSizeOfHeaders, string
 
         public override ArraySegment<byte> WriteMessage(Message message, int maxMessageSize, BufferManager bufferManager, int messageOffset)
         {
-            return WriteMessageInternal(message, maxMessageSize, bufferManager, messageOffset, GenerateStartInfoString(), _boundary, MtomStartUri, writeMessageHeaders: true);
+            return WriteMessageInternal(message, maxMessageSize, bufferManager, messageOffset, GenerateStartInfoString(), _boundary, MtomStartUri, writeMessageHeaders: false);
         }
 
         public override ValueTask<ArraySegment<byte>> WriteMessageAsync(Message message, int maxMessageSize, BufferManager bufferManager, int messageOffset)
         {
-            return new ValueTask<ArraySegment<byte>>(WriteMessageInternal(message, maxMessageSize, bufferManager, messageOffset, GenerateStartInfoString(), _boundary, MtomStartUri, writeMessageHeaders: true));
+            return new ValueTask<ArraySegment<byte>>(WriteMessageInternal(message, maxMessageSize, bufferManager, messageOffset, GenerateStartInfoString(), _boundary, MtomStartUri, writeMessageHeaders: false));
         }
 
         private string GetContentType(out string boundary)
@@ -517,7 +517,7 @@ public override void WriteMessage(Message message, Stream stream)
 
         public override ValueTask WriteMessageAsync(Message message, Stream stream)
         {
-            return WriteMessageInternalAsync(message, stream, GenerateStartInfoString(), _boundary, MtomStartUri, writeMessageHeaders: true);
+            return WriteMessageInternalAsync(message, stream, GenerateStartInfoString(), _boundary, MtomStartUri, writeMessageHeaders: false);
         }
 
         public override IAsyncResult BeginWriteMessage(Message message, Stream stream, AsyncCallback callback, object state)