mcs/class/referencesource/System/compmod/system/componentmodel/AsyncOperation.cs

   1 //------------------------------------------------------------------------------
   2 // <copyright file="AsyncOperation.cs" company="Microsoft">
   3 //     Copyright (c) Microsoft Corporation.  All rights reserved.
   4 // </copyright>
   5 //------------------------------------------------------------------------------
   6
   7 namespace System.ComponentModel
   8 {
   9     using System.Security.Permissions;
  10     using System.Threading;
  11
  12     [HostProtection(SharedState = true)]
  13     public sealed class AsyncOperation
  14     {
  15         private SynchronizationContext syncContext;
  16         private object userSuppliedState;
  17         private bool alreadyCompleted;
  18
  19         /// <summary>
  20         ///     Constructor. Protected to avoid unwitting usage - AsyncOperation objects
  21         ///     are typically created by AsyncOperationManager calling CreateOperation.
  22         /// </summary>
  23         private AsyncOperation(object userSuppliedState, SynchronizationContext syncContext)
  24         {
  25             this.userSuppliedState = userSuppliedState;
  26             this.syncContext = syncContext;
  27             this.alreadyCompleted = false;
  28             this.syncContext.OperationStarted();
  29         }
  30
  31         /// <summary>
  32         ///     Destructor. Guarantees that [....] context will always get notified of completion.
  33         /// </summary>
  34         ~AsyncOperation()
  35         {
  36             if (!alreadyCompleted && syncContext != null)
  37             {
  38                 syncContext.OperationCompleted();
  39             }
  40         }
  41
  42         public object UserSuppliedState
  43         {
  44             get { return userSuppliedState; }
  45         }
  46
  47         /// <include file='doc\AsyncOperation.uex' path='docs/doc[@for="AsyncOperation.SynchronizationContext"]/*' />
  48         public SynchronizationContext SynchronizationContext
  49         {
  50             get
  51             {
  52                 return syncContext;
  53             }
  54         }
  55
  56         public void Post(SendOrPostCallback d, object arg)
  57         {
  58             VerifyNotCompleted();
  59             VerifyDelegateNotNull(d);
  60             syncContext.Post(d, arg);
  61         }
  62
  63         public void PostOperationCompleted(SendOrPostCallback d, object arg)
  64         {
  65             Post(d, arg);
  66             OperationCompletedCore();
  67         }
  68
  69         public void OperationCompleted()
  70         {
  71             VerifyNotCompleted();
  72             OperationCompletedCore();
  73         }
  74
  75         private void OperationCompletedCore()
  76         {
  77             try
  78             {
  79                 syncContext.OperationCompleted();
  80             }
  81             finally
  82             {
  83                 alreadyCompleted = true;
  84                 GC.SuppressFinalize(this);
  85             }
  86         }
  87
  88         private void VerifyNotCompleted()
  89         {
  90             if (alreadyCompleted)
  91             {
  92                 throw new InvalidOperationException(SR.GetString(SR.Async_OperationAlreadyCompleted));
  93             }
  94         }
  95
  96         private void VerifyDelegateNotNull(SendOrPostCallback d)
  97         {
  98             if (d == null)
  99             {
 100                 throw new ArgumentNullException(SR.GetString(SR.Async_NullDelegate), "d");
 101             }
 102         }
 103
 104         /// <summary>
 105         ///     Only for use by AsyncOperationManager to create new AsyncOperation objects
 106         /// </summary>
 107         internal static AsyncOperation CreateOperation(object userSuppliedState, SynchronizationContext syncContext)
 108         {
 109             AsyncOperation newOp = new AsyncOperation(userSuppliedState, syncContext);
 110             return newOp;
 111         }
 112     }
 113 }
 114