Forced cancellation of async wrapped sync task

Question

I have code which calls an external lib synchronous operation, which can take a very long time to finish. I can't rewrite this lib, and there is not a method to stop the operation. Is there any solution to stop this task after some timeout?

I have tried this code, but it does not work not as I expected. It awaits until the calculation is not completed.

How can I solve this task?

 private static async Task<ResultData> GetResultAsync(string fileName)
    {
        var timeoutSource = new CancellationTokenSource(new TimeSpan(0, 5, 0)); 
        try
        {
            return await Task.Run(() =>
            {
                var result = ExternLib.Calculate(fileName);
                if (result == null)
                {
                    throw new CalculationException(fileName);
                }
                return result;
            },
                timeoutSource.Token
            ).ConfigureAwait(false);
        }
        catch (AggregateException e)
        {
            SomeCode(e);
        }
        catch (OperationCanceledException e)
        {
            SomeCode2(e);
        }
        catch (Exception e)
        {
            SomeCode3(e);
        }
        return await Task.FromResult<ResultData>(null).ConfigureAwait(false);
    }

Answer 1

Create two tasks, one which does the work, and one which acts as a timer:

var workTask = Task.Run(() => // etc );
var timerTask = Task.Delay(TimeSpan.FromMinutes(10));

The wait for either task to complete:

var completedTask = Task.WaitAny(new[] { workTask, timerTask });

Then, if completedTask is the timer task, your timeout has expired, and you can take appropriate action: whether or not you can stop the long running task depends on how it's structured, but you do know you can stop waiting for it.