AsyncCompletedEventHandler Delegate
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AsyncCompletedEventHandler Delegate


Represents the method that will handle the MethodNameCompleted event of an asynchronous operation.

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

[HostProtectionAttribute(SecurityAction.LinkDemand, SharedState = true)]
public delegate void AsyncCompletedEventHandler(
	object sender,
	AsyncCompletedEventArgs e


Type: System.Object

The source of the event.

Type: System.ComponentModel.AsyncCompletedEventArgs

An System.ComponentModel.AsyncCompletedEventArgs that contains the event data.

When you create an AsyncCompletedEventHandler delegate, you identify the method that will handle the event. To associate the event with your event handler, add an instance of the delegate to the event. The event-handler method is called whenever the event occurs, unless you remove the delegate. For more information about event-handler delegates, see NIB: Events and Delegates.

For an asynchronous method, called MethodName, in your component, you will have a corresponding MethodNameCompleted event, and an optional MethodNameCompletedEventArgs class.

For a component that supports multiple concurrent invocations of its asynchronous methods, the client can supply a unique token, or task ID, to distinguish which asynchronous task is raising particular events. The client's AsyncCompletedEventHandler can read the AsyncCompletedEventArgs.UserState property to determine which task is reporting completion. Your implementation should use the System.ComponentModel.AsyncOperationManager to create an System.ComponentModel.AsyncOperation that associates the client's task IDs with pending asynchronous tasks.

For a code example of the AsyncCompletedEventHandler delegate, see the example in the System.ComponentModel.AsyncCompletedEventArgs class.

Universal Windows Platform
Available since 4.5
.NET Framework
Available since 2.0
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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