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.NET Framework Class Library
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.

Inheritance Hierarchy
SystemObject
  System.Windows.ThreadingDispatcherTimer

Namespace:   System.Windows.Threading
Assembly:  WindowsBase (in WindowsBase.dll)
XMLNS for XAML: Not mapped to an xmlns.
Syntax
Public Class DispatcherTimer
public class DispatcherTimer
public ref class DispatcherTimer
type DispatcherTimer =  class end
public class DispatcherTimer

The DispatcherTimer type exposes the following members.

Constructors
  NameDescription
Public method DispatcherTimerInitializes a new instance of the DispatcherTimer class.
Public method DispatcherTimer(DispatcherPriority)Initializes a new instance of the DispatcherTimer class which processes timer events at the specified priority.
Public method DispatcherTimer(DispatcherPriority, Dispatcher)Initializes a new instance of the DispatcherTimer class which runs on the specified Dispatcher at the specified priority.
Public method DispatcherTimer(TimeSpan, DispatcherPriority, EventHandler, Dispatcher)Initializes a new instance of the DispatcherTimer class which uses the specified time interval, priority, event handler, and Dispatcher.
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Properties
  NameDescription
Public property DispatcherGets the Dispatcher associated with this DispatcherTimer.
Public property IntervalGets or sets the period of time between timer ticks.
Public property IsEnabledGets or sets a value that indicates whether the timer is running.
Public property TagGets or sets a user-defined data object.
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Methods
  NameDescription
Public method Equals(Object)Determines whether the specified object is equal to the current object. (Inherited from Object.)
Protected method FinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public method GetHashCodeServes as the default hash function. (Inherited from Object.)
Public method GetTypeGets the Type of the current instance. (Inherited from Object.)
Protected method MemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public method StartStarts the DispatcherTimer.
Public method StopStops the DispatcherTimer.
Public method ToStringReturns a string that represents the current object. (Inherited from Object.)
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Events
  NameDescription
Public event TickOccurs when the timer interval has elapsed.
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Remarks

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.TimersTimer is used in a WPF application, it is worth noting that the System.TimersTimer 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.TimersTimer 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.

Examples

The following example creates a DispatcherTimer that updates the contents of a Label and calls the InvalidateRequerySuggested method on the CommandManager.

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 Threading.DispatcherTimer()
			AddHandler dispatcherTimer.Tick, AddressOf dispatcherTimer_Tick
			dispatcherTimer.Interval = New TimeSpan(0,0,1)
			dispatcherTimer.Start()
//  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 Sub dispatcherTimer_Tick(ByVal sender As Object, ByVal e As EventArgs)
			' Updating the Label which displays the current second
			lblSeconds.Content = Date.Now.Second

			' Forcing the CommandManager to raise the RequerySuggested event
			CommandManager.InvalidateRequerySuggested()
		End Sub
//  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();
}
Version Information

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1
Thread Safety
Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.