Winform FormBorderStyle.None时，支持改变窗体大小

没有边框了，没法拖动大小？

//FormBorderStyle.None时，支持改变窗体大小
       # region 支持改变窗体大小
        private const int Guying_HTLEFT = 10;
        private const int Guying_HTRIGHT = 11;
        private const int Guying_HTTOP = 12;
        private const int Guying_HTTOPLEFT = 13;
        private const int Guying_HTTOPRIGHT = 14;
        private const int Guying_HTBOTTOM = 15;
        private const int Guying_HTBOTTOMLEFT = 0x10;
        private const int Guying_HTBOTTOMRIGHT = 17;

        protected override void WndProc(ref Message m)
        {
            switch (m.Msg)
            {
                case 0x0084:
                    base.WndProc(ref m);
                    Point vPoint = new Point((int)m.LParam&0xFFFF,(int)m.LParam >> 16&0xFFFF);
                    vPoint = PointToClient(vPoint);
                    if (vPoint.X <= 5)
                        if (vPoint.Y <= 5)
                            m.Result = (IntPtr)Guying_HTTOPLEFT;
                        else if (vPoint.Y >= ClientSize.Height - 5)
                            m.Result = (IntPtr)Guying_HTBOTTOMLEFT;
                        else
                            m.Result = (IntPtr)Guying_HTLEFT;
                    else if (vPoint.X >= ClientSize.Width - 5)
                        if (vPoint.Y <= 5)
                            m.Result = (IntPtr)Guying_HTTOPRIGHT;
                        else if (vPoint.Y >= ClientSize.Height - 5)
                            m.Result = (IntPtr)Guying_HTBOTTOMRIGHT;
                        else
                            m.Result = (IntPtr)Guying_HTRIGHT;
                    else if (vPoint.Y <= 5)
                        m.Result = (IntPtr)Guying_HTTOP;
                    else if (vPoint.Y >= ClientSize.Height - 5)
                        m.Result = (IntPtr)Guying_HTBOTTOM;
                    break;
                case 0x0201://鼠标左键按下的消息
        m.Msg = 0x00A1; //更改消息为非客户区按下鼠标
                    m.LParam = IntPtr.Zero; //默认值
                    m.WParam = new IntPtr(2); //鼠标放在标题栏内
                    base.WndProc(ref m);
                    break;
                default:
                    base.WndProc(ref m);

                    break;
            }
        }
        #endregion