C# 改变无边框窗体尺寸大小的方法

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const int htleft = 10;
const int htright = 11;
const int httop = 12;
const int httopleft = 13;
const int httopright = 14;
const int htbottom = 15;
const int htbottomleft = 0x10;
const int 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)httopleft;
                else if (vpoint.y >= clientsize.height - 5)
                    m.result = (intptr)htbottomleft;
                else m.result = (intptr)htleft;
            else if (vpoint.x >= clientsize.width - 5)
                if (vpoint.y <= 5)
                    m.result = (intptr)httopright;
                else if (vpoint.y >= clientsize.height - 5)
                    m.result = (intptr)htbottomright;
                else m.result = (intptr)htright;
            else if (vpoint.y <= 5)
                m.result = (intptr)httop;
            else if (vpoint.y >= clientsize.height - 5)
                m.result = (intptr)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;
    }
}