Use request body content type instead of default one

src/RestSharp/RestRequestExtensions.cs

@@ -18,30 +18,25 @@
 using RestSharp.Serialization;
 using RestSharp.Serializers;
 
-namespace RestSharp
-{
-    internal static class RestRequestExtensions
-    {
+namespace RestSharp {
+    internal static class RestRequestExtensions {
         internal static void SerializeRequestBody(
-            this IRestRequest request,
+            this IRestRequest                        request,
             IDictionary<DataFormat, IRestSerializer> restSerializers,
-            params ISerializer[] serializers
-        )
-        {
+            params ISerializer[]                     serializers
+        ) {
             var body = request.Parameters.FirstOrDefault(p => p.Type == ParameterType.RequestBody);
             if (body == null) return;
 
-            if (body.DataFormat == DataFormat.None)
-            {
+            if (body.DataFormat == DataFormat.None) {
                 request.Body = new RequestBody(body.ContentType, body.Name, body.Value);
                 return;
             }
 
             var contentType       = body.ContentType ?? ContentType.FromDataFormat[body.DataFormat];
             var requestSerializer = serializers.FirstOrDefault(x => x != null && x.ContentType == contentType);
 
-            if (requestSerializer != null)
-            {
+            if (requestSerializer != null) {
                 request.Body = new RequestBody(
                     requestSerializer.ContentType,
                     requestSerializer.ContentType,
@@ -52,14 +47,13 @@ params ISerializer[] serializers
 
             if (!restSerializers.TryGetValue(body.DataFormat, out var serializer))
                 throw new InvalidDataContractException(
-                    $"Can't find serializer for content type {body.DataFormat}"
+                    $"Can't find serializer for data type {body.DataFormat}"
                 );
 
-            request.Body = new RequestBody(serializer.ContentType, serializer.ContentType, serializer.Serialize(body));
+            request.Body = new RequestBody(body.ContentType ?? serializer.ContentType, serializer.ContentType, serializer.Serialize(body)!);
         }
 
-        internal static void AddBody(this IHttp http, RequestBody requestBody)
-        {
+        internal static void AddBody(this IHttp http, RequestBody requestBody) {
             // Only add the body if there aren't any files to make it a multipart form request
             // If there are files or AlwaysMultipartFormData = true, then add the body to the HTTP Parameters
             if (requestBody.Value == null) return;
@@ -68,19 +62,17 @@ internal static void AddBody(this IHttp http, RequestBody requestBody)
                 ? requestBody.ContentType
                 : requestBody.Name;
 
-            if (!http.AlwaysMultipartFormData && !http.Files.Any())
-            {
+            if (!http.AlwaysMultipartFormData && !http.Files.Any()) {
                 var val = requestBody.Value;
 
                 if (val is byte[] bytes)
                     http.RequestBodyBytes = bytes;
                 else
                     http.RequestBody = requestBody.Value.ToString();
             }
-            else
-            {
+            else {
                 http.Parameters.Add(new HttpParameter(requestBody.Name, requestBody.Value, requestBody.ContentType));
             }
         }
     }
-}
+}

test/RestSharp.Tests/UrlBuilderTests.cs

@@ -299,7 +299,7 @@ public void Should_build_uri_using_selected_encoding() {
         var client = new RestClient("http://example.com/resource");
 
         var expectedDefaultEncoding  = new Uri("http://example.com/resource?town=Hiller%C3%B8d");
-        var expectedIso89591Encoding = new Uri("http://example.com/resource?town=Hiller%F8d");
+        var expectedIso89591Encoding = new Uri("http://example.com/resource?town=Hiller%f8d");
         Assert.Equal(expectedDefaultEncoding, client.BuildUri(request));
         // now changing encoding
         client.Encoding = Encoding.GetEncoding("ISO-8859-1");