silverlight 获取控件坐标 没有canvas

        void t_GotFocus(object sender, RoutedEventArgs e)

        {

            var tb = sender as TextBox;

            var gt = tb.TransformToVisual(null);

            Point p = gt.Transform(new Point(0, 0));

            MessageBox.Show(p.X + " " + p.Y);

        }