Provides data for the MethodNameCompleted event.
Assembly: System (in System.dll)
Thetype exposes the following members.
|AsyncCompletedEventArgs||Initializes a new instance of the class.|
|AsyncCompletedEventArgs(Exception, Boolean, Object)||Initializes a new instance of the class.|
|Equals(Object)||Determines whether the specified Object is equal to the current Object. (Inherited from Object.)|
|Finalize||Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)|
|GetHashCode||Serves as a hash function for a particular type. (Inherited from Object.)|
|GetType||Gets the Type of the current instance. (Inherited from Object.)|
|MemberwiseClone||Creates a shallow copy of the current Object. (Inherited from Object.)|
|RaiseExceptionIfNecessary||Raises a user-supplied exception if an asynchronous operation failed.|
|ToString||Returns a string that represents the current object. (Inherited from Object.)|
If you are using a class that implements the event-based asynchronous pattern that is described in the Event-based Asynchronous Pattern Overview topic of the .NET Framework documentation, 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 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 canceled.
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 have to track these tokens, known as task IDs, as their corresponding asynchronous tasks start and complete.Notes to Inheritors
You may want to communicate to clients more information about the outcome of an asynchronous operation than supports. In this case, you can derive a custom class from the class and provide additional private instance variables and corresponding read-only public properties. Call the RaiseExceptionIfNecessary method before you return the property value, in case the operation was canceled or an error occurred.
The following code example demonstrates how to derive a custom class from to pass additional information back to the client from an asynchronous operation. This code example is part of a larger example provided for the System.ComponentModel.AsyncOperationManager class.
' Define a custom Completed-event arguments class allowing ' the data gathered by GetPersons to be returned. Public Class GetPersonsCompletedEventArgs Inherits AsyncCompletedEventArgs Private m_dataListValue As List(Of Person) Public Sub New _ (ByVal dataList As List(Of Person), _ ByVal exception As Exception, _ ByVal cancelled As Boolean, _ ByVal userState As Object) MyBase.New(exception, cancelled, userState) m_dataListValue = dataList End Sub Public ReadOnly Property DataListValue() As List(Of Person) Get Me.RaiseExceptionIfNecessary() Return m_dataListValue End Get End Property End Class
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