Gintaras Gintaras - 9 days ago 7
C# Question

C# Task.WaitAll() Cancelation with Error handling

I have a problem.
I try to run multiple long running tasks. If one fails I wanna cancel all other tasks and get the failure exception.
The example given below.
I wanna catch AggregateException with Exception thrown by

throw new Exception("FailureTask");


But instead of AggregateException I am catching OperationCanceledException, because I wanna cancel all other task.

[TestMethod]
public void TestParallelTaskCancelation()
{
var cancellationTokenSource = new CancellationTokenSource();
Task[] tasks =
{
Task.Factory.StartNew(DummyTask, cancellationTokenSource, cancellationTokenSource.Token),
Task.Factory.StartNew(DummyTask, cancellationTokenSource, cancellationTokenSource.Token),
Task.Factory.StartNew(DummyTask, cancellationTokenSource, cancellationTokenSource.Token),
Task.Factory.StartNew(DummyTask, cancellationTokenSource, cancellationTokenSource.Token),
Task.Factory.StartNew(FailureTask, cancellationTokenSource, cancellationTokenSource.Token)
};

try
{
Task.WaitAll(tasks, cancellationTokenSource.Token);
}
catch (OperationCanceledException e)
{
Console.WriteLine(e.GetaAllMessages());
}
catch (AggregateException e)
{
Console.WriteLine(e.GetaAllMessages());
}
}

private void DummyTask(object o)
{
var cancellationToken = (CancellationTokenSource)o;
while (true)
{
Thread.Sleep(10000);
if (cancellationToken.IsCancellationRequested)
{
cancellationToken.Token.ThrowIfCancellationRequested();
}
}
}

private void FailureTask(object o)
{
var cancellationToken = (CancellationTokenSource)o;

var executionTask = Task.Factory.StartNew(() =>
{
Thread.Sleep(1000);
throw new Exception("FailureTask");
}, cancellationToken.Token);

executionTask.ContinueWith(t =>
{
cancellationToken.Cancel(false);
throw new Exception(t.Exception.GetaAllMessages());
}, TaskContinuationOptions.OnlyOnFaulted);

if (executionTask.Wait(10 * 1000, cancellationToken.Token)) return;
//timeout !!!
throw new Exception("The limit 'Max Seconds Per Query' has been exceeded!!!");
}`


Please help.

Ive Ive
Answer

This works for me

public static async void TestParallelTaskCancelation()
    {
        var cancellationTokenSource = new CancellationTokenSource();
        Task[] tasks =
        {
        Task.Factory.StartNew(DummyTask, cancellationTokenSource, cancellationTokenSource.Token),
        Task.Factory.StartNew(DummyTask, cancellationTokenSource, cancellationTokenSource.Token),
        Task.Factory.StartNew(DummyTask, cancellationTokenSource, cancellationTokenSource.Token),
        Task.Factory.StartNew(DummyTask, cancellationTokenSource, cancellationTokenSource.Token),
        Task.Factory.StartNew(FailureTask, cancellationTokenSource, cancellationTokenSource.Token)
        };

        try
        {
           await Task.WhenAll(tasks);
        }
        catch (OperationCanceledException e)
        {
            Console.WriteLine(e.ToString());
        }
        catch (AggregateException e)
        {
            Console.WriteLine(e.ToString());
        }
    }