DispatcherTimer behavior in WP7 application

Question

I am writing an audio recording application for WP7. I have a DispatcherTimer object in my ViewModel class, that when the recording is happening, counts the elapsed seconds to show the length of the recording to a user. I have the following problem with the app:

The tick interval for the DispatcherTimer is set to one second (1000) ms.

When I press the start button, the DispatcherTimer starts. When I press the stop button, the DispatcherTimers thread exits. (in a second!, thought I didn't intend it to be that way))

If I do press the start button after pressing stop to swiftly (less then a second inbetween), my DispatcherTimer fails to start again, since it hasn't yet stopped. (it's thread hasn't exited)

Basically, my biggest concern is why does DispatcherTimer has to wait until it's time for its tick, to realize that it has been stopped, and the thread it created to perform ticks in has to exit?

How can I work around this problem? Thank you.

Answer 1

DispatcherTimers are not guaranteed to execute exactly when the time interval occurs, but they are guaranteed to not execute before the time interval occurs. This is because DispatcherTimer operations are placed on the DispatcherTimer queue like other operations. When the DispatcherTimer operation executes is dependent on the other jobs in the queue and their priorities.

Reference: http://msdn.microsoft.com/en-us/library/system.windows.threading.dispatchertimer(v=VS.95).aspx

You should better use a System.Threading.Timer, which is a timer class that fires on a separate thread. This is good for purely numerical timing, where you're not trying to update the UI, etc.