问如何检测windows phone 8中轴控件内滑动时的水平变化

EN

public TakeTourPage()
{
    InitializeComponent();
    GestureListener gestureListener = GestureService.GetGestureListener(ContentPanel);
    gestureListener.DragCompleted += gestureListener_DragCompleted;
}

void gestureListener_DragCompleted(object sender, DragCompletedGestureEventArgs e)
{

    // User flicked towards left
    if (e.HorizontalVelocity < 0)
    {
    }

    // User flicked towards right
    if (e.HorizontalVelocity > 0)
    {
    }
 }