C# 控件移動位置

private Point mouse_offset;

        private void picDot_MouseDown(object sender, MouseEventArgs e)
        {
            mouse_offset = new Point(-e.X, -e.Y);
        }
         
        private void picDot_MouseMove(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                Point mousePos = Control.MousePosition;
                mousePos.Offset(mouse_offset.X, mouse_offset.Y);
                ((Control)sender).Location = ((Control)sender).Parent.PointToClient(mousePos);
            }
        }