AsyncCompletedEventArgs.UserState Property
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 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.
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(),
result);
if (lvi != null) {
lvi.set_BackColor(Color.get_Pink());
lvi.set_Tag(null);
}
}
else {
if (e.get_Error() != null) {
String result = "Error";
ListViewItem lvi = UpdateListViewItem((Guid)e.get_UserState(),
result);
if (lvi != null) {
lvi.set_BackColor(Color.get_Red());
lvi.set_ForeColor(Color.get_White());
lvi.set_Tag(null);
}
}
else {
boolean result = e.get_IsPrime();
ListViewItem lvi = UpdateListViewItem((Guid)e.get_UserState(),
result, e.get_FirstDivisor());
if (lvi != null) {
lvi.set_BackColor(Color.get_LightGray());
lvi.set_Tag(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.