AsyncCompletedEventArgs Class

Provides data for the MethodNameCompleted event.

Namespace:  System.ComponentModel
Assembly:  System (in System.dll)

[HostProtectionAttribute(SecurityAction.LinkDemand, SharedState = true)]
public class AsyncCompletedEventArgs : EventArgs

NoteNote:

The HostProtectionAttribute attribute applied to this type or member has the following Resources property value: SharedState. The HostProtectionAttribute does not affect desktop applications (which are typically started by double-clicking an icon, typing a command, or entering a URL in a browser). For more information, see the HostProtectionAttribute class or SQL Server Programming and Host Protection Attributes.

If you are using a class that implements the Event-based Asynchronous Pattern Overview, the class will provide a MethodNameCompleted event. If you add an instance of the System.ComponentModel.AsyncCompletedEventHandler delegate to the event, you will receive information about the outcome of asynchronous operations in the AsyncCompletedEventArgs parameter of the corresponding event-handler method.

The client application's event-handler delegate can check the Cancelled property to determine if the asynchronous task was cancelled.

The client application's event-handler delegate can check the Error property to determine if an exception occurred during execution of the asynchronous task.

If the class supports multiple asynchronous methods, or multiple calls to the same asynchronous method, you can determine which task raised the MethodNameCompleted event by checking the value of the UserState property. Your code will need to track these tokens, known as task IDs, as their corresponding asynchronous tasks start and complete.

Notes to Inheritors:

Classes that follow the Event-based Asynchronous Pattern can raise events to alert clients about the status of pending asynchronous operations. If the class provides a MethodNameCompleted event, you can use the AsyncCompletedEventArgs to tell clients about the outcome of asynchronous operations.

You may want to communicate to clients more information about the outcome of an asynchronous operation than an AsyncCompletedEventArgs accommodates. In this case, you can derive your own class from the AsyncCompletedEventArgs class and provide additional private instance variables and corresponding read-only public properties. Call the RaiseExceptionIfNecessary method before returning the property value, in case the operation was canceled or an error occurred.

The following code example demonstrates using an AsyncOperation to track the lifetime of asynchronous operations. This code example is part of a larger example provided for the System.ComponentModel.AsyncOperationManager class.

using System;
using System.Collections;
using System.Collections.Specialized;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Globalization;
using System.Threading;
using System.Windows.Forms;


...


// This event handler updates the ListView control when the
// PrimeNumberCalculator raises the CalculatePrimeCompleted
// event. The ListView item is updated with the appropriate
// outcome of the calculation: Canceled, Error, or result.
private void primeNumberCalculator1_CalculatePrimeCompleted(
    object sender, 
    CalculatePrimeCompletedEventArgs e)
{
    Guid taskId = (Guid)e.UserState;

    if (e.Cancelled)
    {   
        string result = "Canceled";

        ListViewItem lvi = UpdateListViewItem(taskId, result);

        if (lvi != null)
        {
            lvi.BackColor = Color.Pink;
            lvi.Tag = null;
        }
    }
    else if (e.Error != null)
    {
        string result = "Error";

        ListViewItem lvi = UpdateListViewItem(taskId, result);

        if (lvi != null)
        {
            lvi.BackColor = Color.Red;
            lvi.ForeColor = Color.White;
            lvi.Tag = null;
        }
    }
    else
    {   
        bool result = e.IsPrime;

        ListViewItem lvi = UpdateListViewItem(
            taskId, 
            result, 
            e.FirstDivisor);

        if (lvi != null)
        {
            lvi.BackColor = Color.LightGray;
            lvi.Tag = null;
        }
    }
}

System.Object
  System.EventArgs
    System.ComponentModel.AsyncCompletedEventArgs
      System.ComponentModel.RunWorkerCompletedEventArgs
      System.Deployment.Application.CheckForUpdateCompletedEventArgs
      System.Deployment.Application.DownloadApplicationCompletedEventArgs
      System.Deployment.Application.DownloadFileGroupCompletedEventArgs
      System.Deployment.Application.GetManifestCompletedEventArgs
      System.Net.DownloadDataCompletedEventArgs
      System.Net.DownloadStringCompletedEventArgs
      System.Net.NetworkInformation.PingCompletedEventArgs
      System.Net.OpenReadCompletedEventArgs
      System.Net.OpenWriteCompletedEventArgs
      System.Net.PeerToPeer.Collaboration.CreateContactCompletedEventArgs
      System.Net.PeerToPeer.Collaboration.InviteCompletedEventArgs
      System.Net.PeerToPeer.Collaboration.RefreshDataCompletedEventArgs
      System.Net.PeerToPeer.Collaboration.SubscribeCompletedEventArgs
      System.Net.PeerToPeer.ResolveCompletedEventArgs
      System.Net.UploadDataCompletedEventArgs
      System.Net.UploadFileCompletedEventArgs
      System.Net.UploadStringCompletedEventArgs
      System.Net.UploadValuesCompletedEventArgs
      System.Speech.Recognition.EmulateRecognizeCompletedEventArgs
      System.Speech.Recognition.LoadGrammarCompletedEventArgs
      System.Speech.Recognition.RecognizeCompletedEventArgs
      System.Speech.Synthesis.PromptEventArgs
      System.Web.Services.Protocols.InvokeCompletedEventArgs
      System.Windows.Documents.GetPageCompletedEventArgs
      System.Windows.Documents.GetPageNumberCompletedEventArgs
      System.Windows.Documents.GetPageRootCompletedEventArgs
      System.Windows.Documents.Serialization.WritingCompletedEventArgs
      System.Windows.Xps.Serialization.XpsSerializationCompletedEventArgs

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0

.NET Compact Framework

Supported in: 3.5

XNA Framework

Supported in: 3.0, 2.0, 1.0
Was this page helpful?
(1500 characters remaining)
Thank you for your feedback

Community Additions

ADD
Show:
© 2014 Microsoft