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AsyncCompletedEventArgs.UserState Property

Gets the unique identifier for the asynchronous task.

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

property Object^ UserState {
	Object^ get ();
/** @property */
public Object get_UserState ()

public function get UserState () : Object

Not applicable.

Property Value

An object reference that uniquely identifies the asynchronous task; otherwise, a null reference (Nothing in Visual Basic) if no value has been set.

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

The value of this property is set during the original call to the asynchronous method that started the task.

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.

No code example is currently available or this language may not be supported.
import System.*;
import System.Collections.*;
import System.Collections.Specialized.*;
import System.ComponentModel.*;
import System.Data.*;
import System.Drawing.*;
import System.Threading.*;
import System.Windows.Forms.*;


    private void primeNumberCalculator1_CalculatePrimeCompleted(Object sender,
        CalculatePrimeCompletedEventArgs e)
        Guid guid = (Guid)e.get_UserState();
        if (e.get_Cancelled()) {
            String result = "Cancelled";
            ListViewItem lvi = UpdateListViewItem((Guid)e.get_UserState(),
            if (lvi != null) {
        else {
            if (e.get_Error() != null) {
                String result = "Error";
                ListViewItem lvi = UpdateListViewItem((Guid)e.get_UserState(),
                if (lvi != null) {
            else {
                boolean result = e.get_IsPrime();
                ListViewItem lvi = UpdateListViewItem((Guid)e.get_UserState(),
                    result, e.get_FirstDivisor());
                if (lvi != null) {
    } //primeNumberCalculator1_CalculatePrimeCompleted

Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0

XNA Framework

Supported in: 1.0

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