Gets the unique identifier for the asynchronous task.
Assembly: System (in System.dll)
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 theproperty. 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.
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
Available since 8
Available since 2.0
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Available since 8.1