C# Winform去掉窗体灰色边框，以及实现窗体可拖动边框改变大小

private const int WM_NCLBUTTONDBLCLK = 163;
        private const int WM_NCHITTEST = 132;
        /// <summary>
        /// 边框改变大小
        /// </summary>
        /// <param name="m"></param>
        protected override void WndProc(ref Message m)
        {
            switch (m.Msg)
            {
                case WM_NCLBUTTONDBLCLK://WM_NCLBUTTONDBLCLK=163 <0xA3>拦截鼠标非客户区左键双击消息,决定窗体是否最大化显示
                    if (this.MaximizeBox)
                    {
                        base.WndProc(ref m);
                        this.Invalidate();
                    }
                    return;
                case WM_NCHITTEST://WM_NCHITTEST=132 <0x84> 
                    base.WndProc(ref m);//如果去掉这一行代码,窗体将失去MouseMove..等事件
                    //Point lpint = new Point((int)m.LParam);//可以得到鼠标坐标,这样就可以决定怎么处理这个消息了,是移动窗体,还是缩放,以及向哪向的缩放
                    //if (lpint.Y < 30)
                    //    m.Result = (IntPtr)0x2;//托动HTCAPTION=2 <0x2>
                    if (WindowState != FormWindowState.Maximized)
                    {
                        Point p2 = this.PointToClient(MousePosition);//鼠标相对于窗体的坐标
                        //当然可以托动也可以改变大小了
                        //label1.Text = p2.X + "," + p2.Y;
                        //HTLEFT=10 <0xA> 左边框
                        if (p2.X < 5 && p2.Y > 5 && p2.Y < this.Height - 5)
                            m.Result = (IntPtr)0xA;
                        else if (p2.Y < 5 && p2.X > 5 && p2.X < this.Width - 5)
                            m.Result = (IntPtr)0xC;
                        //HTTOP=12 <0xC> 上边框                   
                        else if (p2.X < 5 && p2.Y < 5)
                            m.Result = (IntPtr)0xD;
                        //HTTOPLEFT=13 <0xD>
                        else if (p2.X >= this.Width - 5 && p2.Y < 5)
                            m.Result = (IntPtr)0xE;
                        //HTTOPRIGHT=14 <0xE> 
                        else if (p2.X > this.Width - 5 && p2.Y > 5 && p2.Y < this.Height - 5)
                            m.Result = (IntPtr)0xB;
                        //HTRIGHT=11 <0xB>
                        else if (p2.Y >= this.Height - 5 && p2.X > 5 && p2.X < this.Width - 5)
                            m.Result = (IntPtr)0xF;
                        //HTBOTTOM=15 <0xF>
                        else if (p2.X < 5 && p2.Y >= this.Height - 5)
                            m.Result = (IntPtr)0x10;
                        //HTBOTTOMLEFT=16 <0x10>
                        else if (p2.X > this.Width - 5 && p2.Y >= this.Height - 5)
                            m.Result = (IntPtr)0x11;
                        //HTBOTTOMRIGHT=17 <0x11>

                        //HTBORDER=18 <0x12>

                        //HTMINBUTTON=8 <0x8> 最小化按钮

                        //HTMAXBUTTON=9 <0x9> 最大化按钮
                        //HTCLOSE=20 <0x14> 关闭按钮
                    }
                    return;
                default:
                    base.WndProc(ref m);
                    return;
            }
        }