c#窗体去掉borderstyle进行拖动

private void BaseCForm_Load(object sender, EventArgs e)
        {
            DrawStyle();

this.panel1.MouseDown += new MouseEventHandler(panel1_MouseDown);
            this.panel1.MouseUp += new MouseEventHandler(panel1_MouseUp);
            this.panel1.MouseMove += new MouseEventHandler(panel1_MouseMove);
        }

private void panel1_MouseDown(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                mouseOff = new Point(-e.X, -e.Y);
                leftFlag = true;
            }

}

private void panel1_MouseUp(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                leftFlag = false;
            }
        }

private void panel1_MouseMove(object sender, MouseEventArgs e)
        {
            if (leftFlag)
            {
                Point mouseSet = Control.MousePosition;
                mouseSet.Offset(mouseOff.X, mouseOff.Y);
                if (sender is Panel)
                {
                    ((System.Windows.Forms.Panel)sender).Parent.Location = mouseSet;
                }
            }

}

[DllImport("user32.dll")]
        public static extern bool ReleaseCapture();
        [DllImport("user32.dll")]
        public static extern bool SendMessage(IntPtr hwnd, int wMsg, int wParam, int lParam);

private const int WM_SYSCOMMAND = 0x0112;//点击窗口左上角那个图标时的系统信息
        private const int WM_MOVING = 0x216;//鼠标移动消息
        private const int SC_MOVE = 0xF010;//移动信息
        private const int HTCAPTION = 0x0002;//表示鼠标在窗口标题栏时的系统信息
        private const int WM_NCHITTEST = 0x84;//鼠标在窗体客户区（除了标题栏和边框以外的部分）时发送的消息
        private const int HTCLIENT = 0x1;//表示鼠标在窗口客户区的系统消息
        private const int SC_MAXIMIZE = 0xF030;//最大化信息
        private const int SC_MINIMIZE = 0xF020;//最小化信息

protected override void WndProc(ref Message m)
        {
            switch (m.Msg)
            {
                case WM_MOVING: //如果鼠标移                 
                    base.WndProc(ref m);//调用基类的窗口过程——WndProc方法处理这个消息
                    if (m.Result == (IntPtr)HTCLIENT)//如果返回的是HTCLIENT
                    {
                        m.Result = (IntPtr)HTCAPTION;//把它改为HTCAPTION
                        return;//直接返回退出方法
                    }
                    break;
            }
            base.WndProc(ref m);//如果不是鼠标移动或单击消息就调用基类的窗口过程进行处理

}

protected override void OnMouseMove(MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                ReleaseCapture();
                SendMessage(this.Handle, WM_SYSCOMMAND, SC_MOVE + HTCAPTION, 0);
            }
            base.OnMouseMove(e);
        }