Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.ServiceModel/System/ServiceModel/Dispatcher/TaskExtensions.cs

@@ -0,0 +1,43 @@
+// <copyright>
+//   Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>
+
+namespace System.ServiceModel.Dispatcher
+{
+    using System;
+    using System.Diagnostics;
+    using System.Linq;
+    using System.Reflection;
+    using System.Runtime;
+    using System.Runtime.Diagnostics;
+    using System.Threading.Tasks;
+
+    /// <summary>
+    /// Extension methods for Task and its generic counterpart(Task of T)
+    /// </summary>
+    internal static class TaskExtensions
+    {
+        private const string TaskAsAsyncResultMethodName = "AsAsyncResult";
+        private static MethodInfo taskAsAsyncResultMethodInfo;
+
+        public static MethodInfo TaskAsAsyncResultMethodInfo
+        {
+            get
+            {
+                if (taskAsAsyncResultMethodInfo == null)
+                {
+                    taskAsAsyncResultMethodInfo = typeof(System.Runtime.TaskExtensions).GetMethods().Where(m =>
+                                                   m.IsGenericMethod && m.Name == TaskAsAsyncResultMethodName).First();
+                    Fx.Assert(taskAsAsyncResultMethodInfo != null, "taskAsAsyncResultMethodInfo should not be null.");
+                }
+
+                return taskAsAsyncResultMethodInfo;
+            }
+        }
+
+        public static MethodInfo MakeGenericMethod(Type genericArgument)
+        {
+            return TaskExtensions.TaskAsAsyncResultMethodInfo.MakeGenericMethod(genericArgument);
+        }
+    }
+}