mcs/class/System.Web.Mvc2/System.Web.Mvc/Async/AsyncUtil.cs

   1 /* ****************************************************************************\r
   2  *\r
   3  * Copyright (c) Microsoft Corporation. All rights reserved.\r
   4  *\r
   5  * This software is subject to the Microsoft Public License (Ms-PL). \r
   6  * A copy of the license can be found in the license.htm file included \r
   7  * in this distribution.\r
   8  *\r
   9  * You must not remove this notice, or any other, from this software.\r
  10  *\r
  11  * ***************************************************************************/\r
  12 \r
  13 namespace System.Web.Mvc.Async {\r
  14     using System;\r
  15     using System.Threading;\r
  16 \r
  17     internal static class AsyncUtil {\r
  18 \r
  19         public static void WaitForAsyncResultCompletion(IAsyncResult asyncResult, HttpApplication app) {\r
  20             // based on HttpServerUtility.ExecuteInternal()\r
  21 \r
  22             if (!asyncResult.IsCompleted) {\r
  23                 // suspend app lock while waiting, else might deadlock\r
  24                 bool needToRelock = false;\r
  25 \r
  26                 try {\r
  27                     // .NET 2.0+ will not allow a ThreadAbortException to be thrown while a\r
  28                     // thread is inside a finally block, so this pattern ensures that the\r
  29                     // value of 'needToRelock' is correct.\r
  30                     try { }\r
  31                     finally {\r
  32                         Monitor.Exit(app);\r
  33                         needToRelock = true;\r
  34                     }\r
  35 \r
  36                     WaitHandle waitHandle = asyncResult.AsyncWaitHandle;\r
  37 \r
  38                     if (waitHandle != null) {\r
  39                         waitHandle.WaitOne();\r
  40                     }\r
  41                     else {\r
  42                         while (!asyncResult.IsCompleted) {\r
  43                             Thread.Sleep(1);\r
  44                         }\r
  45                     }\r
  46                 }\r
  47                 finally {\r
  48                     if (needToRelock) {\r
  49                         Monitor.Enter(app);\r
  50                     }\r
  51                 }\r
  52             }\r
  53         }\r
  54 \r
  55         public static AsyncCallback WrapCallbackForSynchronizedExecution(AsyncCallback callback, SynchronizationContext syncContext) {\r
  56             if (callback == null || syncContext == null) {\r
  57                 return callback;\r
  58             }\r
  59 \r
  60             AsyncCallback newCallback = delegate(IAsyncResult asyncResult) {\r
  61                 if (asyncResult.CompletedSynchronously) {\r
  62                     callback(asyncResult);\r
  63                 }\r
  64                 else {\r
  65                     // Only take the application lock if this request completed asynchronously,\r
  66                     // else we might end up in a deadlock situation.\r
  67                     syncContext.Sync(() => callback(asyncResult));\r
  68                 }\r
  69             };\r
  70 \r
  71             return newCallback;\r
  72         }\r
  73 \r
  74     }\r
  75 }\r