What if a timer can not finish all its works before the new cycle time arrives?
If you're using System.Threading.Timer or System.Timers.Timer, the timer will tick again, starting a new thread. See https://stackoverflow.com/a/10442117/56778 for a way to avoid that problem.
If you're using System.Windows.Forms.Timer, then a new tick won't occur until the previous one is finished processing.
Put your code in a Monitor.TryEnter()
object timeCheck= new object();void Timer(){ Monitor.TryEnter(timeCheck) { //Code that might take too long //... Monitor.Exit(); }}
to prevent reentrancy, you might use a static boolean that tells wether the function is allready beeing executed. User a try/Catch/finally and set this boolean to false in the finally to ensure that the boolean does not remain false if you made a mistake in code or if the code failed.
For a faster timer, reentrancy should be prevented by using semaphore (mutex).