询问 是否关闭窗体

protected override void WndProc(ref Message m)
        {
            const int WM_SYSCOMMAND = 0x0112;
            const int SC_CLOSE = 0xF060;
            if (m.Msg == WM_SYSCOMMAND && (int)m.WParam == SC_CLOSE)
            {
                //窗体最小化
                //this.WindowState = FormWindowState.Maximized;
                //return;

                //询问是否关闭窗体
                if (DialogResult.No == MessageBox.Show("确定要关闭吗？", "提示", MessageBoxButtons.YesNo, MessageBoxIcon.Question))
                {
                    return;
                }
            }

            base.WndProc(ref m);
        }