Question

I’m working on a Windows Service with a timer to schedule a job each interval of time.
It seems that the timer elapsed event is fired more than one time.

Here a code sample:

private static System.Timers.Timer _timer = new System.Timers.Timer();

protected override void OnStart(string[] args)
{
      _timer.Elapsed += new System.Timers.ElapsedEventHandler(OnTimedEvent);
      _timer.Interval = 1000;
      _timer.Enabled = true;
      _timer.Start();
}

private void OnTimedEvent(object source, System.Timers.ElapsedEventArgs e)
{
      _timer.Enabled = false;
      _timer.Stop();

      //Do the job

      _timer.Enabled = true;
      _timer.Start();
}

Can you help me?
Thank you

Answer 1

The signal to raise the Elapsed event is always queued for execution
on a ThreadPool thread, so the event-handling method might run on one
thread at the same time that a call to the Stop method runs on another
thread. This might result in the Elapsed event being raised after the
Stop method is called. The code example in the next section shows one
way to work around this race condition.

Quoted from: Timer.Stop Method. Please see the code sample on the page.