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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)
XMLNS for XAML: http://schemas.microsoft.com/winfx/2006/xaml/presentation, http://schemas.microsoft.com/netfx/2007/xaml/presentation
public event DragDeltaEventHandler DragDelta
<object DragDelta="DragDeltaEventHandler" .../>

Identifier field

DragDeltaEvent

Routing strategy

Bubbling

Delegate

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.

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

Supported in: 4.5.1, 4.5, 4, 3.5, 3.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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