C#创建可拖动按钮

private Button b;
private Point location;
private void button1_MouseDown(object sender, MouseEventArgs e)
        {
            location = e.Location;
            b = sender as Button;
                       
        }

private void button1_MouseMove(object sender, MouseEventArgs e)
        {

            int pos_x, pos_y;

            if (e.Button == MouseButtons.Left)
            {
                pos_x = b.Location.X + (e.X - location.X);
                pos_y = b.Location.Y + (e.Y - location.Y);
                b.Location = new Point(pos_x, pos_y);
            }      
           
        }