Winform 窗口拖动

把窗口边框去掉后，窗口拖动问题：

 private Point mouseOffset; //记录鼠标指针的坐标 
        private bool isMouseDown = false; //记录鼠标按键是否按下 

        private void Form1_MouseDown(object sender, MouseEventArgs e)
        {
            int xOffset;
            int yOffset;

            if (e.Button == MouseButtons.Left)
            {
                xOffset = -e.X - SystemInformation.FrameBorderSize.Width;
                yOffset = -e.Y - SystemInformation.CaptionHeight -
                SystemInformation.FrameBorderSize.Height;
                mouseOffset = new Point(xOffset, yOffset);
                isMouseDown = true;
            } 
        }

        private void Form1_MouseMove(object sender, MouseEventArgs e)
        {
            if (isMouseDown)
            {
                Point mousePos = Control.MousePosition;
                mousePos.Offset(mouseOffset.X, mouseOffset.Y);
                Location = mousePos;
            } 
        }

        private void Form1_MouseUp(object sender, MouseEventArgs e)
        {
            // 修改鼠标状态isMouseDown的值 
            // 确保只有鼠标左键按下并移动时，才移动窗体 
            if (e.Button == MouseButtons.Left)
            {
                isMouseDown = false;
            } 
        }