Wait for System.Threading.Timer Callbacks to Complete before Exiting Program

Question

I have a List<System.Threading.Timer>. Each Timer fires at a configurable interval (default 10 minutes). All call the same callback method (with a different parameter). The callback method can take several seconds to complete it's work.

When the program terminates, it looks like execution of the callback method is immediately halted (am I seeing that correctly?).

How can I elegantly wait for any currently-executing callback methods to complete before exiting the program?

Answer 1

You can Dispose all timers with WaitHandler parameter. This handler will be signaled only when callback method is completed (as spec says: "The timer is not disposed until all currently queued callbacks have completed.")

void WaitUntilCompleted(List<Timer> myTimers)
{
    List<WaitHandle> waitHnd = new List<WaitHandle>();
    foreach (var timer in myTimers)
    {
        WaitHandle h = new AutoResetEvent(false);
        if(!timer.Dispose(h)) throw new Exception("Timer already disposed.");
        waitHnd.Add(h);
    }
    WaitHandle.WaitAll(waitHnd.ToArray());
}

Edit: @Peter underlined importance of the Dispose method return value. It returns false when timer already disposed. To make sure this solutions stays reliable, I modified it to throw exception when Timer already disposed as we can't control in such case when its callback finishes, despite earlier disposal callback might still be running!