How to cancel a Task using CancellationToken?
10,796
You're swallowing the exception, thus the task is flagged as finished as you actually handle the exception and it doesn't propagate outwards.
Instead, don't catch the exception inside the delegate, catch it outside:
void Main()
{
CancellationTokenSource src = new CancellationTokenSource();
CancellationToken ct = src.Token;
ct.Register(() => Console.WriteLine("Abbruch des Tasks"));
Task t = Task.Run(() =>
{
System.Threading.Thread.Sleep(1000);
ct.ThrowIfCancellationRequested();
}, ct);
src.Cancel();
try
{
t.Wait();
}
catch (AggregateException e)
{
// Don't actually use an empty catch clause, this is
// for the sake of demonstration.
}
Console.WriteLine("Canceled: {0} . Finished: {1} . Error: {2}",
t.IsCanceled, t.IsCompleted, t.IsFaulted);
}
Author by
Netherstorm
Updated on June 05, 2022Comments
-
Netherstorm almost 2 years
So I've this code:
//CancelationToken CancellationTokenSource src = new CancellationTokenSource(); CancellationToken ct = src.Token; ct.Register(() => Console.WriteLine("Abbruch des Tasks")); //Task Task t = new Task(() => { System.Threading.Thread.Sleep(1000); if (ct.IsCancellationRequested) { try { //Throw ct.ThrowIfCancellationRequested(); } catch (OperationCanceledException) { Console.WriteLine( "ThrowIfCancellationRequested() liefert eben eine Exception"); } } }, ct); //Run Task and Cancel t.Start(); src.CancelAfter(350); t.Wait(); // Get Information Console.WriteLine("Canceled: {0} . Finished: {1} . Error: {2}", t.IsCanceled, t.IsCompleted, t.IsFaulted);
So in this case I canceled my Task but my output in the end is: "Canceled: False . Finished: True . Error: False"
In my opinion it should be "Canceled:True . Finished:False". Why do I get this result? Because I try to catch the exception?
I've tried it without the try - catch block, but then my program stops because of the OperationCanceledException. Can somebody help me?