wpf 绘制矩形

            TouchPoint touchPoint = e.GetTouchPoint(mywin);
            p2 = touchPoint.Position;

            RectangleGeometry rec = new RectangleGeometry();
            rec.Rect = new Rect(p1, p2);

            Path path = new Path();
            path.Fill = Brushes.LemonChiffon;
            path.Stroke = Brushes.Black;
            path.StrokeThickness = 1;
            path.Data = rec;
            canvas1.Children.Add(path);