C# – Implement C# Generic Timeout

asynchronouscc#-3.0multithreadingtimeout

I am looking for good ideas for implementing a generic way to have a single line (or anonymous delegate) of code execute with a timeout.

TemperamentalClass tc = new TemperamentalClass();
tc.DoSomething();  // normally runs in 30 sec.  Want to error at 1 min

I'm looking for a solution that can elegantly be implemented in many places where my code interacts with temperamental code (that I can't change).

In addition, I would like to have the offending "timed out" code stopped from executing further if possible.

Best Answer

The really tricky part here was killing the long running task through passing the executor thread from the Action back to a place where it could be aborted. I accomplished this with the use of a wrapped delegate that passes out the thread to kill into a local variable in the method that created the lambda.

I submit this example, for your enjoyment. The method you are really interested in is CallWithTimeout. This will cancel the long running thread by aborting it, and swallowing the ThreadAbortException:

Usage:

class Program
{

    static void Main(string[] args)
    {
        //try the five second method with a 6 second timeout
        CallWithTimeout(FiveSecondMethod, 6000);

        //try the five second method with a 4 second timeout
        //this will throw a timeout exception
        CallWithTimeout(FiveSecondMethod, 4000);
    }

    static void FiveSecondMethod()
    {
        Thread.Sleep(5000);
    }

The static method doing the work:

    static void CallWithTimeout(Action action, int timeoutMilliseconds)
    {
        Thread threadToKill = null;
        Action wrappedAction = () =>
        {
            threadToKill = Thread.CurrentThread;
            try
            {
                action();
            }
            catch(ThreadAbortException ex){
               Thread.ResetAbort();// cancel hard aborting, lets to finish it nicely.
            }
        };

        IAsyncResult result = wrappedAction.BeginInvoke(null, null);
        if (result.AsyncWaitHandle.WaitOne(timeoutMilliseconds))
        {
            wrappedAction.EndInvoke(result);
        }
        else
        {
            threadToKill.Abort();
            throw new TimeoutException();
        }
    }

}
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