Dispatcher Class (System.Windows.Threading)

.NET Framework Class Library for Silverlight

Dispatcher Class

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

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

Syntax

Visual Basic (Declaration)

<CLSCompliantAttribute(True)> _
Public NotInheritable Class Dispatcher

Visual Basic (Usage)

Dim instance As Dispatcher

[CLSCompliantAttribute(true)]
public sealed class Dispatcher

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.

Visual Basic

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.");
}

Inheritance Hierarchy

System..::.Object
System.Windows.Threading..::.Dispatcher

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.

Platforms

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

Reference

Dispatcher Members

System.Windows.Threading Namespace