public void Remove()
{
if (_topLeftHelperPoint != null)
{
_layer.Shapes = _layer.Shapes.Remove(_topLeftHelperPoint);
_topLeftHelperPoint = null;
}
if (_bottomRightHelperPoint != null)
{
_layer.Shapes = _layer.Shapes.Remove(_bottomRightHelperPoint);
_bottomRightHelperPoint = null;
}
_layer.Invalidate();
}
}