AsyncCompletedEventArgs Class
Provides data for the MethodNameCompleted event.
Assembly: System (in System.dll)
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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.
Imports System Imports System.Collections Imports System.Collections.Specialized Imports System.ComponentModel Imports System.Drawing Imports System.Globalization Imports System.Threading Imports 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 Sub primeNumberCalculator1_CalculatePrimeCompleted( _ ByVal sender As Object, _ ByVal e As CalculatePrimeCompletedEventArgs) _ Handles primeNumberCalculator1.CalculatePrimeCompleted Dim taskId As Guid = CType(e.UserState, Guid) If e.Cancelled Then Dim result As String = "Canceled" Dim lvi As ListViewItem = UpdateListViewItem( _ taskId, _ result) If (lvi IsNot Nothing) Then lvi.BackColor = Color.Pink lvi.Tag = Nothing End If ElseIf e.Error IsNot Nothing Then Dim result As String = "Error" Dim lvi As ListViewItem = UpdateListViewItem( _ taskId, result) If (lvi IsNot Nothing) Then lvi.BackColor = Color.Red lvi.ForeColor = Color.White lvi.Tag = Nothing End If Else Dim result As Boolean = e.IsPrime Dim lvi As ListViewItem = UpdateListViewItem( _ taskId, _ result, _ e.FirstDivisor) If (lvi IsNot Nothing) Then lvi.BackColor = Color.LightGray lvi.Tag = Nothing End If End If End Sub
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
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.
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