Fixed Proxy when using MultipartForm with byte[] (#473)

* wip

* ByteArrayContentHelper

* ByteArrayContentHelperTests

src/WireMock.Net/Http/ByteArrayContentHelper.cs

@@ -0,0 +1,30 @@
+using System.Net.Http;
+using System.Net.Http.Headers;
+using JetBrains.Annotations;
+using WireMock.Validation;
+
+namespace WireMock.Http
+{
+    internal static class ByteArrayContentHelper
+    {
+        /// <summary>
+        /// Creates a ByteArrayContent object.
+        /// </summary>
+        /// <param name="content">The byte[] content (cannot be null)</param>
+        /// <param name="contentType">The ContentType (can be null)</param>
+        /// <returns>ByteArrayContent</returns>
+        internal static ByteArrayContent Create([NotNull] byte[] content, [CanBeNull] MediaTypeHeaderValue contentType)
+        {
+            Check.NotNull(content, nameof(content));
+
+            var byteContent = new ByteArrayContent(content);
+            if (contentType != null)
+            {
+                byteContent.Headers.Remove(HttpKnownHeaderNames.ContentType);
+                byteContent.Headers.ContentType = contentType;
+            }
+
+            return byteContent;
+        }
+    }
+}

src/WireMock.Net/Http/HttpRequestMessageHelper.cs

@@ -1,10 +1,10 @@
-using JetBrains.Annotations;
-using Newtonsoft.Json;
-using System;
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Net.Http;
 using System.Net.Http.Headers;
+using JetBrains.Annotations;
+using Newtonsoft.Json;
 using WireMock.Types;
 using WireMock.Validation;
 
@@ -29,7 +29,7 @@ namespace WireMock.Http
             switch (requestMessage.BodyData?.DetectedBodyType)
             {
                 case BodyType.Bytes:
-                    httpRequestMessage.Content = new ByteArrayContent(requestMessage.BodyData.BodyAsBytes);
+                    httpRequestMessage.Content = ByteArrayContentHelper.Create(requestMessage.BodyData.BodyAsBytes, contentType);
                     break;
 
                 case BodyType.Json:

src/WireMock.Net/Owin/Mappers/OwinRequestMapper.cs

@@ -64,6 +64,7 @@ namespace WireMock.Owin.Mappers
                     ContentEncoding = contentEncodingHeader?.FirstOrDefault(),
                     DecompressGZipAndDeflate = !options.DisableRequestBodyDecompressing.GetValueOrDefault(false)
                 };
+
                 body = await BodyParser.Parse(bodyParserSettings);
             }
 

src/WireMock.Net/Util/BodyParser.cs

@@ -130,7 +130,7 @@ namespace WireMock.Util
                     data.Encoding = encoding;
                     data.DetectedBodyType = BodyType.String;
                 }
-
+   
                 return data;
             }