Thumb::DragDelta Event

 

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 DragDeltaEventHandler^ DragDelta {
	void add(DragDeltaEventHandler^ value);
	void remove(DragDeltaEventHandler^ value);
}

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

DragDeltaEvent

Routing strategy

Bubbling

Delegate

DragDeltaEventHandler

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) +
                                e.HorizontalChange);
        Canvas.SetTop(myThumb, Canvas.GetTop(myThumb) +
                                e.VerticalChange);
        changes.Text = "Size: " +
                        myCanvasStretch.Width.ToString() +
                         ", " +
                        myCanvasStretch.Height.ToString();
    }
}

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