Question

I need to create a method for listening to events and waiting for a certain amount of silence before calling another function.

Specifically, I am listening to a directory for file updates. When a file change occurs, my “directoryUpdate” function is called. From there I add the file to a list and create a thread called “timerThread” which sleeps for 2 seconds. When that thread is done sleeping, it calls a “gatherFinished” function.

But since directoryUpdate gets called 10 times all at once if 10 files change, it would launch 10 threads which seems like a bad way of doing this.

In the end I want a list of the file changes that occurred within 2 seconds of each other. I figure if there is a way to reset the sleep time to 2 seconds every time a change occurs and wait for the 2 seconds to finish, then I will have what I need. But there is no way to reset the timer as far as I know.

What is the best way of doing this?

UPDATE
Thanks for all your great answers. I am sorry for putting emphasis on getting the list of files. The event (file change) should not matter. I meant to focus on making sure the call to “gatherFinished” happens once at the right time – 2 seconds after all events in question have stopped firing. My question is on the nature of waiting, not on the nature of files or collections.

Answer 1

You could just use an AutoResetEvent and wait 2 seconds on it. If the event is triggered then you loop and wait another 2 seconds.

        AutoResetEvent resetTimer = new AutoResetEvent(false);

        ...

        private void TimerJob()
        {
            ...

            // The thread will sleep and loop until 
            // 2 seconds elapse without directory changes 
            while (resetTimer.WaitOne(2000)) {}

            ...
        }

        private void ResetTimer()
        {
            resetTimer.Set();
        }

NOTE: I didn’t put any code to specify you how to synchronize the thread that will receive the directory changes and the timer thread. You will have to do that youself.