public void BeginDrag(IDragSource source, UIElement uiElement, Point pt)
{
_source = source;
WindowHandler.BeginDrag(pt);
DragDetect(uiElement, pt);
}
public void BeginDrag(IDragSource source, UIElement uiElement, MouseEventArgs e)
{
_source = source;
WindowHandler.BeginDrag(e);
DragDetect(uiElement, e);
}