Dispatcher.Invoke Method (DispatcherPriority, TimeSpan, Delegate, Object, Object())


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Executes the specified delegate at the specified priority with the specified arguments synchronously on the thread the Dispatcher is associated with.

Namespace:   System.Windows.Threading
Assembly:  WindowsBase (in WindowsBase.dll)

Public Function Invoke (
	priority As DispatcherPriority,
	timeout As TimeSpan,
	method As Delegate,
	arg As Object,
	ParamArray args As Object()
) As Object


Type: System.Windows.Threading.DispatcherPriority

The priority, relative to the other pending operations in the Dispatcher event queue, the specified method is invoked.

Type: System.TimeSpan

The maximum time to wait for the operation to finish.

Type: System.Delegate

A delegate to a method that takes multiple arguments, which is pushed onto the Dispatcher event queue.

Type: System.Object

An object to pass as an argument to the specified method.

Type: System.Object()

An array of objects to pass as arguments to the specified method.

Return Value

Type: System.Object

The return value from the delegate being invoked or null if the delegate has no return value.

Exception Condition

priority is equal to Inactive.


priority is not a valid DispatcherPriority.


method is null.

Arg can be null if an argument is not needed.

In WPF, only the thread that created a DispatcherObject may access that object. For example, a background thread that is spun off from the main UI thread cannot update the contents of a Button that was created on the UI thread. In order for the background thread to access the Content property of the Button, the background thread must delegate the work to the Dispatcher associated with the UI thread. This is accomplished by using either Invoke or BeginInvoke. Invoke is synchronous and BeginInvoke is asynchronous. The operation is added to the event queue of the Dispatcher at the specified DispatcherPriority.

Invoke is a synchronous operation; therefore, control will not return to the calling object until after the callback returns.

.NET Framework
Available since 3.0
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