C# DispatcherTimer Issue

Question

I have an issue with the WPF Timer.

Here's my code :

System.Windows.Threading.DispatcherTimer dispatcherTimer = new System.Windows.Threading.DispatcherTimer();
dispatcherTimer.Tick += new EventHandler(DispatcherTimer_Tick);
dispatcherTimer.Interval = new TimeSpan(0, 0, 1);

As you can see the interval is 1 minute. But when i start my timer, after 1 hour i have a 10 seconde delay. So, i guess it the treatment of my code who make this delay, but i really need a fix timer, without any shift.

Sorry for your eyes !!

First of all, that interval is 1 second, and not 1 minute. Second, try the constructor where you specify the priority `DispatcherTimer a = new DispatcherTimer(DispatcherPriority.Send)` — Nekeniehl, Jun 11 '18 at 09:45
Why are you using a dispatcher timer if you need a fix timer? — Nekeniehl, Jun 11 '18 at 09:53
Try creating a program where all you do is this timer. Then, if you still have the problem, post your code here. — Neil, Jun 11 '18 at 09:53
@DiSiZ - You understand that this is an "interval" meaning when the last handler of the tick completes then the next interval starts? So if the handlers take 0.25 seconds to process then each successive start is 1.25 seconds if the interval is set to 1 second. — Enigmativity, Jun 11 '18 at 09:54
Ive done it Neil, 0 delay when the program is empty, with just the timer — DiSiZ, Jun 11 '18 at 10:11
I was thinking using this : https://msdn.microsoft.com/en-us/library/system.diagnostics.stopwatch.aspx#Fields Look's more accurate — DiSiZ, Jun 11 '18 at 10:45

score 0 · Answer 1 · answered Feb 28 '22 at 10:59

The delay is caused by the WPF GUI thread, which runs all WPF code, like rendering and the DispatcherTimer.Tick event. The rendering has a higher priority than a DispatcherTimer with default priority. So when at the time your Tick is supposed to run also some rendering is needed, the rendering gets executed first and delays your Tick by x milliseconds. This is not too bad, but unfortunately these delays can accumulate over time, if you leave the DispatcherTimer.Interval constant. You can improve the precision of the DispatcherTimer by shortening the DispatcherTimer.Interval for every x milliseconds delay like this:

const int constantInterval = 100;//milliseconds

private void Timer_Tick(object? sender, EventArgs e) {
  var now = DateTime.Now;
  var nowMilliseconds = (int)now.TimeOfDay.TotalMilliseconds;
  var timerInterval = constantInterval - 
   nowMilliseconds%constantInterval + 5;//5: sometimes the tick comes few millisecs early
  timer.Interval = TimeSpan.FromMilliseconds(timerInterval);

For a more detail explanation see my article on CodeProject: Improving the WPF DispatcherTimer Precision

C# DispatcherTimer Issue

1 Answers1