Dispatcher Class

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Provides services for managing the queue of work items for a thread.

Inheritance Hierarchy

System.Object
  System.Windows.Threading.Dispatcher

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

Syntax

'Declaration
<CLSCompliantAttribute(True)> _
Public NotInheritable Class Dispatcher

[CLSCompliantAttribute(true)]
public sealed class Dispatcher

The Dispatcher type exposes the following members.

Methods

	Name	Description
	BeginInvoke(Action)	Executes the specified delegate asynchronously on the thread the Dispatcher is associated with.
	BeginInvoke(Delegate, array<Object[])	Executes the specified delegate asynchronously with the specified array of arguments on the thread the Dispatcher is associated with.
	CheckAccess	Determines whether the calling thread is the thread associated with this Dispatcher.
	Equals(Object)	Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
	GetHashCode	Serves as a hash function for a particular type. (Inherited from Object.)
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	ToString	Returns a string that represents the current object. (Inherited from Object.)

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Remarks

The Dispatcher class currently provides support only for running code on the user interface (UI) thread from a non-UI thread.

You can access the Dispatcher object for the UI thread through the DependencyObject.Dispatcher and ScriptObject.Dispatcher properties. These are instance methods, but instances of these types are frequently inaccessible from non-UI threads. However, the application's Deployment object is a DependencyObject, and it is available on any thread through its Current property.

You can call the CheckAccess method to determine whether the caller is on the UI thread. If the caller is not on the UI thread, you can call BeginInvoke to run the specified delegate on the UI thread.

Examples

The following code example demonstrates how to use this class.

Private Delegate Sub AddTextDelegate(ByVal p As Panel, ByVal text As String)

Private Sub AddText(ByVal p As Panel, ByVal text As String)
    p.Children.Clear()
    Dim t As New TextBlock
    t.Text = text
    p.Children.Add(t)
End Sub

Private Sub TestBeginInvokeWithParameters(ByVal p As Panel)
    If p.Dispatcher.CheckAccess() _
        Then AddText(p, "Added directly.") _
        Else p.Dispatcher.BeginInvoke(New AddTextDelegate( _
            AddressOf AddText), p, "Added by Dispatcher.")
End Sub

private delegate void AddTextDelegate(Panel p, String text);

private void AddText(Panel p, String text)
{
    p.Children.Clear();
    p.Children.Add(new TextBlock { Text = text });
}

private void TestBeginInvokeWithParameters(Panel p)
{
    if (p.Dispatcher.CheckAccess()) AddText(p, "Added directly.");
    else p.Dispatcher.BeginInvoke(
        new AddTextDelegate(AddText), p, "Added by Dispatcher.");
}

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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.

See Also

Reference

System.Windows.Threading Namespace