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DispatcherTimer Class

A timer that is integrated into the Dispatcher queue which is processed at a specified interval of time and at a specified priority.

Namespace:  System.Windows.Threading
Assembly:  WindowsBase (in WindowsBase.dll)
XMLNS for XAML: Not mapped to an xmlns.

public class DispatcherTimer
This managed class is not typically used in XAML.

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

Timers 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 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. For an example of using a System.Timers.Timer, see Disable Command Source via System Timer Sample. 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.

The following example creates a DispatcherTimer that updates the contents of a Label and calls the InvalidateRequerySuggested method on the CommandManager. For the full sample, see Disable Command Source via Dispatcher Timer Sample.

A DispatcherTimer object named dispatcherTimer is created. The event handler dispatcherTimer_Tick is added to the Tick event of dispatcherTimer. The Interval is set to 1 second using a TimeSpan object, and the timer is started.

//  DispatcherTimer setup
dispatcherTimer = new System.Windows.Threading.DispatcherTimer();
dispatcherTimer.Tick += new EventHandler(dispatcherTimer_Tick);
dispatcherTimer.Interval = new TimeSpan(0,0,1);
dispatcherTimer.Start();

The Tick event handler updates a Label that displays the current second, and it calls InvalidateRequerySuggested on the CommandManager.

//  System.Windows.Threading.DispatcherTimer.Tick handler 
// 
//  Updates the current seconds display and calls 
//  InvalidateRequerySuggested on the CommandManager to force  
//  the Command to raise the CanExecuteChanged event. 
private void dispatcherTimer_Tick(object sender, EventArgs e)
{
    // Updating the Label which displays the current second
    lblSeconds.Content = DateTime.Now.Second;

    // Forcing the CommandManager to raise the RequerySuggested event
    CommandManager.InvalidateRequerySuggested();
}

System.Object
  System.Windows.Threading.DispatcherTimer

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0

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