THRIFT-3510 Add HttpTaskAsyncHandler implementation
Client: C#
Author: Adam Connelly <adam.rpconnelly@gmail.com>

This closes #762
diff --git a/lib/csharp/src/TAsyncProcessor.cs b/lib/csharp/src/TAsyncProcessor.cs
new file mode 100644
index 0000000..ab43225
--- /dev/null
+++ b/lib/csharp/src/TAsyncProcessor.cs
@@ -0,0 +1,38 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License 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.
+ */
+
+using System.Threading.Tasks;
+using Thrift.Protocol;
+
+namespace Thrift
+{
+    /// <summary>
+    /// Processes a message asynchronously.
+    /// </summary>
+    public interface TAsyncProcessor
+    {
+        /// <summary>
+        /// Processes the next part of the message.
+        /// </summary>
+        /// <param name="iprot">The input protocol.</param>
+        /// <param name="oprot">The output protocol.</param>
+        /// <returns>true if there's more to process, false otherwise.</returns>
+        Task<bool> ProcessAsync(TProtocol iprot, TProtocol oprot);
+    }
+}