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POCancelling a Task is throwing an exception
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copied!<p>From what I've read about Tasks, the following code should cancel the currently executing task without throwing an exception. I was under the impression that the whole point of task cancellation was to politely "ask" the task to stop without aborting threads.</p> <p>The output from the following program is:</p> <blockquote> <p>Dumping exception</p> <p>[OperationCanceledException]</p> <p>Cancelling and returning last calculated prime.</p> </blockquote> <p>I am trying to avoid any exceptions when cancelling. How can I accomplish this?</p> <pre><code>void Main() { var cancellationToken = new CancellationTokenSource(); var task = new Task<int>(() => { return CalculatePrime(cancellationToken.Token, 10000); }, cancellationToken.Token); try { task.Start(); Thread.Sleep(100); cancellationToken.Cancel(); task.Wait(cancellationToken.Token); } catch (Exception e) { Console.WriteLine("Dumping exception"); e.Dump(); } } int CalculatePrime(CancellationToken cancelToken, object digits) { int factor; int lastPrime = 0; int c = (int)digits; for (int num = 2; num < c; num++) { bool isprime = true; factor = 0; if (cancelToken.IsCancellationRequested) { Console.WriteLine ("Cancelling and returning last calculated prime."); //cancelToken.ThrowIfCancellationRequested(); return lastPrime; } // see if num is evenly divisible for (int i = 2; i <= num/2; i++) { if ((num % i) == 0) { // num is evenly divisible -- not prime isprime = false; factor = i; } } if (isprime) { lastPrime = num; } } return lastPrime; } </code></pre>

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