C# captures the windows shutdown event and does some sample code to do what you want to do before the system shuts down.

C# Capture Windows shutdown events and do some things you want to do before the system shuts down;

Sometimes we may want to record or process some things when Windows shuts down. Here are several methods.

Method one:

        /// <summary>
        /// 窗口过程的回调函数
        /// </summary>
        /// <param name="m"></param>
        protected override void WndProc(ref Message m)
        {
            switch (m.Msg)
            {
                //此消息在OnFormClosing之前
                case WindowsMessage.WM_QUERYENDSESSION:
                    //MessageBox.Show("WndProc.WM_QUERYENDSESSION.我要阻止系统关闭！");
                    //this.Close();
                    //this.Dispose();
                    //Application.Exit();
                    m.Result = (IntPtr)1; //阻止Windows注销、关机或重启
                    break;
                default:
                    break;
            }
            base.WndProc(ref m);
        }

Method two:

        protected override void OnFormClosing(FormClosingEventArgs e)
        {
            switch (e.CloseReason)
            {
                case CloseReason.ApplicationExitCall:
                    e.Cancel = true;
                    MessageBox.Show("拦截关闭要求事件！");
                    break;
                case CloseReason.FormOwnerClosing:
                    e.Cancel = true;
                    MessageBox.Show("拦截自身关闭事件！");
                    break;
                case CloseReason.MdiFormClosing:
                    e.Cancel = true;
                    MessageBox.Show("拦截MDI窗体关闭事件！");
                    break;
                case CloseReason.None:
                    break;
                case CloseReason.TaskManagerClosing:
                    e.Cancel = true;
                    MessageBox.Show("拦截任务管理器关闭事件！");
                    break;
                case CloseReason.UserClosing:
                    
                    //注销或关机会触发此事件；
                    //MessageBox.Show("拦截用户关闭事件！");
                    e.Cancel = false;
                    break;
                case CloseReason.WindowsShutDown:
                    e.Cancel = true;
                    MessageBox.Show("拦截关机事件！");
                    break;
                default:
                    break;
            }

            base.OnFormClosing(e);
        }

Method three:

//当用户试图注销或关闭系统时发生。  
            SystemEvents.SessionEnding += new SessionEndingEventHandler(SystemEvents_SessionEnding);

//下面是系统注销或关闭事件处理程序，  
        private void SystemEvents_SessionEnding(object sender, SessionEndingEventArgs e)
        {
            if (MessageBox.Show(this, "是否允许系统注销！", "系统提示", MessageBoxButtons.YesNo) != DialogResult.Yes)
            {
                e.Cancel = true;
            }
            else
            {
                e.Cancel = false;
            }
            SessionEndReasons reason = e.Reason;
            switch (reason)
            {
                case SessionEndReasons.Logoff:
                    MessageBox.Show("用户正在注销。操作系统继续运行，但启动此应用程序的用户正在注销。");
                    break;
                case SessionEndReasons.SystemShutdown:
                    MessageBox.Show("操作系统正在关闭。");
                    break;
            }
        }
        //如果把上面的事件处理程序修改成如下  
        //private void SystemEvents_SessionEnding(object sender, SessionEndingEventArgs e)  
        //       {  
        //          e.Cancel = true; 
        //   } 

        //那会出现什么情况，你点击开始菜单关机选择注销、关机、或重新启动将会失效，电脑不能正常关机了，进一步的话把程序做成Windows服务，晕，恶作剧？ 

        //SessionEnded事件同上，事件参数类为SessionEndedEventArgs，同SessionEndingEventArgs相比少了Cancel属性，Cancel属性同一些windows下的某些事件差不多，
        比如Form.Closing事件，Control.Validating事件。

        //补充，如果需要获取应用程序需要的系统信息，可以访问System.Windows.Forms.SystemInformation类，这也是一个很有用的类，它提供了一组静态属性。

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