What is difference between Timer and Dispatcher

Dispatcher things

The DispatcherTimer is reevaluated at the top of every Dispatcher loop.

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

If a System.Timers.Timer is used in a WPF application, it is worth noting that the System.Timers.Timer runs on a different thread then the user interface (UI) thread. In order to access objects on the user interface (UI) thread, it is necessary to post the operation onto the Dispatcher of the user interface (UI) thread using Invoke or BeginInvoke. Reasons for using a DispatcherTimer opposed to a System.Timers.Timer are that the DispatcherTimer runs on the same thread as the Dispatcher and a DispatcherPriority can be set on the DispatcherTimer.

A DispatcherTimer will keep an object alive whenever the object’s methods are bound to the timer.

So, the right way to schedule things inside the WPF UI is something like this.

private DispatcherTimer _timer;
timer = new DispatcherTimer(DispatcherPriority.Background);
timer.Interval = TimeSpan.FromMinutes(5);
timer.Tick += delegate { ScheduleUpdate(); };
timer.Start();