Thumb.DragDelta Event


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Occurs one or more times as the mouse changes position when a Thumb control has logical focus and mouse capture.

Namespace:   System.Windows.Controls.Primitives
Assembly:  PresentationFramework (in PresentationFramework.dll)

Public Event DragDelta As DragDeltaEventHandler

The Thumb control receives focus and mouse capture when the user presses the left mouse button while pausing the mouse pointer over the Thumb control. The Thumb control loses mouse capture when the user releases the left mouse button, or when the CancelDrag method is called.

A new DragDelta event occurs each time the mouse position moves on the screen. Therefore, this event can be raised multiple times without a limit when a Thumb control has mouse capture.

Identifier field


Routing strategy




The following example shows how to assign an event handler for the DragDelta event to a Thumb control, and how to define the event handler. For the complete sample, see Thumb Drag Functionality Sample.

<Thumb Name="myThumb" Canvas.Left="80" Canvas.Top="80" Background="Blue" 
      Width="20" Height="20" DragDelta="onDragDelta" 
      DragStarted="onDragStarted" DragCompleted="onDragCompleted"
void onDragDelta(object sender, DragDeltaEventArgs e)
    //Move the Thumb to the mouse position during the drag operation
    double yadjust = myCanvasStretch.Height + e.VerticalChange;
    double xadjust = myCanvasStretch.Width + e.HorizontalChange;
    if ((xadjust >= 0) && (yadjust >= 0))
        myCanvasStretch.Width = xadjust;
        myCanvasStretch.Height = yadjust;
        Canvas.SetLeft(myThumb, Canvas.GetLeft(myThumb) +
        Canvas.SetTop(myThumb, Canvas.GetTop(myThumb) +
        changes.Text = "Size: " +
                        myCanvasStretch.Width.ToString() +
                         ", " +

.NET Framework
Available since 3.0
Available since 2.0
Windows Phone Silverlight
Available since 7.0
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