Avoid creating unnecessary intermediate strings

generator/ServiceClientGeneratorLib/Generators/Marshallers/JsonRPCRequestMarshaller.tt

@@ -93,32 +93,35 @@ namespace <#=this.Config.Namespace #>.Model.Internal.MarshallTransformations
 	if (this.Operation.RequestHasBodyMembers || shouldMarshallPayload)
 	{
 #>
-			using (StringWriter stringWriter = new StringWriter(CultureInfo.InvariantCulture))
-			{
-				JsonWriter writer = new JsonWriter(stringWriter);
-				writer.Validate = false;
+            using (MemoryStream memoryStream = new MemoryStream())
+            {
+                using (StreamWriter streamWriter = new InvariantCultureStreamWriter(memoryStream))
+                {
+                    JsonWriter writer = new JsonWriter(streamWriter);
+				    writer.Validate = false;
 <#		
 		if (shouldMarshallPayload)
 		{
 #>
-				var context = new JsonMarshallerContext(request, writer);
+				    var context = new JsonMarshallerContext(request, writer);
 <#		
-			ProcessStructure(0, "publicRequest." + payload.PropertyName, payload.Shape);
+			ProcessStructure(1, "publicRequest." + payload.PropertyName, payload.Shape);
 		}
 		else
 		{
 #>
-				writer.WriteObjectStart();
-				var context = new JsonMarshallerContext(request, writer);
+				    writer.WriteObjectStart();
+				    var context = new JsonMarshallerContext(request, writer);
 <#		
-				ProcessMembers(1, "publicRequest", this.Operation.RequestBodyMembers);
+				ProcessMembers(2, "publicRequest", this.Operation.RequestBodyMembers);
 #>
-				writer.WriteObjectEnd();
+				    writer.WriteObjectEnd();
 <#
 		}
 #>
-				string snippet = stringWriter.ToString();
-				request.Content = System.Text.Encoding.UTF8.GetBytes(snippet);
+                }
+
+                request.Content = memoryStream.ToArray();
 <#
 					GenerateRequestChecksumHandling(this.Operation, "snippet");
 #>

sdk/src/Core/Amazon.Runtime/Internal/Util/InvariantCultureStreamWriter.cs

@@ -0,0 +1,52 @@
+/*******************************************************************************
+ *  Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *  Licensed under the Apache License, Version 2.0 (the "License"). You may not use
+ *  this file except in compliance with the License. A copy of the License is located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ *  or in the "license" file accompanying this file.
+ *  This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
+ *  CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ *  specific language governing permissions and limitations under the License.
+ * *****************************************************************************
+ *    __  _    _  ___
+ *   (  )( \/\/ )/ __)
+ *   /__\ \    / \__ \
+ *  (_)(_) \/\/  (___/
+ *
+ *  AWS SDK for .NET
+ *  API Version: 2006-03-01
+ *
+ */
+
+using System;
+using System.Globalization;
+using System.IO;
+
+namespace Amazon.Runtime.Internal.Util
+{
+    /// <summary>
+    /// A <see cref="StreamWriter"/> that uses the invariant culture for formatting.
+    /// </summary>
+    public class InvariantCultureStreamWriter : StreamWriter
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="InvariantCultureStreamWriter"/> class with the specified stream.
+        /// </summary>
+        /// <param name="stream">The stream to write to.</param>
+        public InvariantCultureStreamWriter(Stream stream)
+            : base(stream)
+        {
+        }
+
+        /// <inheritdoc/>
+        public override IFormatProvider FormatProvider
+        {
+            get
+            {
+                return CultureInfo.InvariantCulture;
+            }
+        }
+    }
+}