当窗口的formBorderStyle设置为None时，如何实现窗体拖动

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 picCLose_Click(object sender, EventArgs e)

        {

            Application.Exit();

        }

        private void fmLogin_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 fmLogin_MouseMove(object sender, MouseEventArgs e)

        {

            if (isMouseDown)

            {

                Point mousePos = Control.MousePosition;

                mousePos.Offset(mouseOffset.X+5, mouseOffset.Y+30);

                Location = mousePos;

            }

        }

        private void fmLogin_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;

            }

        }