C#怎么让一个button拖动后top,left不要出去panel1，只能在panel1里面。下面的代码怎么修改？？？？

private bool isMove = false;
private int MouseDownX;
private int MouseDownY;


 private void lblCode_MouseMove(object sender, MouseEventArgs e)
  {
  if (isMove)//如果左键按下的话
  {
  ((Button)sender).Location = new Point(((Button)sender).Left + e.X - MouseDownX, ((Button)sender).Top + e.Y - MouseDownY);
  }


 private void lblCode_MouseDown(object sender, MouseEventArgs e)
  {
  isMove = true;
    
  MouseDownX = e.X;
  MouseDownY = e.Y;
    

 
  }
  private void lblCode_MouseUp(object sender, MouseEventArgs e)
  {
  isMove = false;
  }

[ 本帖最后由 宇智波曌 于 2012-5-12 15:49 编辑 ]

在释放鼠标的时候判断一下坐标是否超出，如果超出，重新弹回去。

怎么判断？能加点代码吗？

大致的写了一下
private Point oldPoint;
        private void btnMove_MouseDown(object sender, MouseEventArgs e)
        {
            oldPoint = e.Location;
            Console.WriteLine("startX={0},startY={1},btnX={2},btnY={3}", e.Location.X, e.Location.Y, btnMove.Location.X, btnMove.Location.Y);
        }

        private void btnMove_MouseUp(object sender, MouseEventArgs e)
        {
            btnMove.Cursor = Cursors.Default;
            if (e.Button == MouseButtons.Left)
            {
                Point newPosition = btnMove.Location;
                newPosition.Offset(e.Location.X - oldPoint.X, e.Location.Y - oldPoint.Y);
                if (new Rectangle(0, 0, panel1.Width - btnMove.Width, panel1.Height - btnMove.Height).Contains(newPosition))
                {
                    btnMove.Location = newPosition;
                }
                else
                {
                    //MessageBox.Show("Out range!");
                }
            }
        }

        private void btnMove_MouseMove(object sender, MouseEventArgs e)
        {
            btnMove.Cursor = Cursors.Arrow;
            if (e.Button == MouseButtons.Left)
            {
                Point newPosition = btnMove.Location;
                newPosition.Offset(e.Location.X - oldPoint.X, e.Location.Y - oldPoint.Y);
                if (new Rectangle(0, 0, panel1.Width - btnMove.Width, panel1.Height - btnMove.Height).Contains(newPosition))
                {
                    btnMove.Location = newPosition;
                }
                else
                {
                    //MessageBox.Show("Out range!");
                }
            }
        }