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Dispatcher.BeginInvoke Method (DispatcherPriority, Delegate, Object, Object[])

Executes the specified delegate asynchronously at the specified priority and with the specified array of arguments on the thread the Dispatcher is associated with.

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

[BrowsableAttribute(false)]
public DispatcherOperation BeginInvoke(
	DispatcherPriority priority,
	Delegate method,
	Object arg,
	params Object[] args
)

Parameters

priority
Type: System.Windows.Threading.DispatcherPriority

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

method
Type: System.Delegate

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

arg
Type: System.Object

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

args
Type: System.Object[]

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

Return Value

Type: System.Windows.Threading.DispatcherOperation
An object, which is returned immediately after BeginInvoke is called, that can be used to interact with the delegate as it is pending execution in the Dispatcher queue.

ExceptionCondition
ArgumentNullException

method is null.

InvalidEnumArgumentException

DispatcherPriority is not a valid priority.

The arg parameter can be null if no arguments are needed.

BeginInvoke returns a DispatcherOperation object that can be used to interact with the delegate when the delegate is in the event queue.

The DispatcherOperation object returned by BeginInvoke can be used in several ways to interact with the specified delegate, such as:

  • Changing the DispatcherPriority of the delegate as it is pending execution in the event queue.

  • Removing the delegate from the event queue.

  • Waiting for the delegate to return.

  • Obtaining the value that the delegate returns after it is executed.

BeginInvoke is asynchronous; therefore, control returns immediately to the calling object after it is called.

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.

If multiple BeginInvoke calls are made at the same DispatcherPriority, they will be executed in the order the calls were made.

If BeginInvoke is called on a Dispatcher that has shut down, the status property of the returned DispatcherOperation is set to Aborted.

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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