Task.IsCancelled doesn't work

Question

I've got the following sample code:

static class Program
{
    static void Main()
    {
        var cts = new CancellationTokenSource();

        var task = Task.Factory.StartNew(
            () =>
                {
                    try
                    {
                        Console.WriteLine("Task: Running");
                        Thread.Sleep(5000);
                        Console.WriteLine("Task: ThrowIfCancellationRequested");
                        cts.Token.ThrowIfCancellationRequested();
                        Thread.Sleep(2000);
                        Console.WriteLine("Task: Completed");
                    }
                    catch (Exception exception)
                    {
                        Console.WriteLine("Task: " + exception.GetType().Name);
                        throw;
                    }
                }).ContinueWith(t => Console.WriteLine("ContinueWith: cts.IsCancellationRequested = {0}, task.IsCanceled = {1}, task.Exception = {2}", cts.IsCancellationRequested, t.IsCanceled, t.Exception == null ? "null" : t.Exception.GetType().Name));

        Thread.Sleep(1000);

        Console.WriteLine("Main: Cancel");
        cts.Cancel();

        try
        {
            Console.WriteLine("Main: Wait");
            task.Wait();
        }
        catch (Exception exception)
        {
            Console.WriteLine("Main: Catch " + exception.GetType().Name);
        }

        Console.WriteLine("Main: task.IsCanceled = {0}", task.IsCanceled);
        Console.WriteLine("Press any key to exit...");

        Console.ReadLine();
    }
}

The output is:

• Task: Running
• Main: Cancel
• Main: Wait
• Task: ThrowIfCancellationRequested
• Task: OperationCanceledException
• ContinueWith: cts.IsCancellationRequested = True, task.IsCanceled = False, task.Exception = AggregateException
• Main: task.IsCanceled = False
• Press any key to exit...

If I remove ContinueWith, then the output is:

• Task: Running
• Main: Cancel
• Main: Wait
• Task: ThrowIfCancellationRequested
• Task: OperationCanceledException
• Main: Catch AggregateException
• Main: task.IsCanceled = False
• Press any key to exit...

I don't understand, why task.IsCanceled returns false in both cases?

And why exception is rethrown only without ContinueWith?

---

What I'm trying to achieve is an uniform and simple way for waiting for task completion and a property that will indicate if task was cancelled or not.

Answer 1

I think you are not cancelling the task itself, but just throwing an exception from a task. Try using StartNew(Action action,CancellationToken cancellationToken) instead of StartNew(Action action). You can also add cancellation token as a parameter to ContinueWith.