static void RemovePreviewAdorner()
{
if (_overlayElt != null)
{
AdornerLayer.GetAdornerLayer(GetTopContainer()).Remove(_overlayElt);
_overlayElt = null;
}
}
static void CreatePreviewAdorner(UIElement adornedElt, UIElement feedbackUI)
{
// Clear if there is an existing preview adorner
RemovePreviewAdorner();
var layer = AdornerLayer.GetAdornerLayer(GetTopContainer());
_overlayElt = new DropPreviewAdorner(feedbackUI, adornedElt);
layer.Add(_overlayElt);
}