Dispatcher.PushFrame(DispatcherFrame) Method

Definition

Namespace:

System.Windows.Threading

Assembly:

WindowsBase.dll

Enters an execute loop.

public:
 static void PushFrame(System::Windows::Threading::DispatcherFrame ^ frame);

public static void PushFrame (System.Windows.Threading.DispatcherFrame frame);

static member PushFrame : System.Windows.Threading.DispatcherFrame -> unit

Public Shared Sub PushFrame (frame As DispatcherFrame)

Parameters

frame

DispatcherFrame

The frame for the dispatcher to process.

Exceptions

ArgumentNullException

frame is null.

InvalidOperationException

HasShutdownFinished is true

-or-

frame is running on a different Dispatcher.

-or-

Dispatcher processing has been disabled.

Examples

The following example shows how to use a DispatcherFrame to achieve similar results as the Windows Forms DoEvents method.

public void DoEvents()
{
    DispatcherFrame frame = new DispatcherFrame();
    Dispatcher.CurrentDispatcher.BeginInvoke(DispatcherPriority.Background,
        new DispatcherOperationCallback(ExitFrame), frame);
    Dispatcher.PushFrame(frame);
}

public object ExitFrame(object f)
{
    ((DispatcherFrame)f).Continue = false;
   
    return null;
}

<SecurityPermissionAttribute(SecurityAction.Demand, Flags := SecurityPermissionFlag.UnmanagedCode)>
Public Sub DoEvents()
    Dim frame As New DispatcherFrame()
    Dispatcher.CurrentDispatcher.BeginInvoke(DispatcherPriority.Background, New DispatcherOperationCallback(AddressOf ExitFrame), frame)
    Dispatcher.PushFrame(frame)
End Sub

Public Function ExitFrame(ByVal f As Object) As Object
    CType(f, DispatcherFrame).Continue = False

    Return Nothing
End Function

Remarks

A DispatcherFrame represents a loop that processes pending work items.

The Dispatcher processes the work item queue in a loop. The loop is referred to as a frame. The initial loop is typically initiated by the application by calling Run.

PushFrame enters a loop represented by the parameter frame. At each iteration of the loop, the Dispatcher will check the Continue property on the DispatcherFrame class to determine whether the loop should continue or if it should stop.

DispatcherFrame allows for the Continue property to be set explicitly and it respects the HasShutdownStarted property on the Dispatcher. This means when the Dispatcher starts to shut down, frames that use the default DispatcherFrame implementation will exit, which enables all nested frames to exit.

See also

• ExitAllFrames()