C# System.Threading.TimerCallback在使用实体框架时仅触发一次

我正在开发一个简单的应用程序，每60秒检查一次数据库。我使用

System.Threading.TimerCallback

来实现这一点，但是，当我运行应用程序时，它只会滴答一次

代码如下：

private void Form1_Load(object sender, EventArgs e)
    {
        // Create the delegate for the Timer type. 
        System.Threading.TimerCallback timeCB = new System.Threading.TimerCallback(d);

        // Establish timer settings. 
        System.Threading.Timer t = new System.Threading.Timer(
          timeCB,     // The TimerCallback delegate object. 
          null,       // Any info to pass into the called method (null for no info). 
          0,          // Amount of time to wait before starting (in milliseconds). 
          1000);      // Interval of time between calls (in milliseconds). 
    }

    void m(object o)
    {
        System.Media.SystemSounds.Hand.Play();
        SReminderEntities ctx = new SReminderEntities();

        var jobs = (from m in ctx.Messages
                    select m).ToList();

        var seljobs = from j in jobs
                      where j.RemindeTime.Date == DateTime.Now.Date
                            && j.RemindeTime.Hour == DateTime.Now.Hour
                            && j.RemindeTime.Minute == DateTime.Now.Minute
                      select j;

        foreach (var j in seljobs)
        {
           // SendGmail("iReminder", j.Text, new string[] { j.User.Email }, "iReminderSender@Gmail.com");
            //this.sendSMS(j.User.Mobile, j.Text);
            System.Media.SystemSounds.Hand.Play();
        }//foreach
    }

    void d(object o)
    {
        MessageBox.Show("Test");
    }

---

当我调用

d

时，它会工作，但

m

只运行一次。问题是什么？我如何解决？谢谢。

System.Threading.Timer类要求您维护自己对它的引用。它本身没有任何根数据结构来保持实例的可访问性。因此，如果您自己不保留引用，垃圾收集器将回收对象，丢弃您的计时器

尝试在表单类中创建一个私有实例字段，并将引用存储在那里

另见，其中部分内容如下：

只要使用计时器，就必须保留对它的引用。与任何托管对象一样，当没有对计时器的引用时，计时器将接受垃圾收集。计时器仍处于活动状态这一事实并不妨碍对其进行收集

---

一旦完成表单加载，它就会自行处理。您需要创建对计时器对象的窗体级引用，然后在Form_Load上使用所需参数重新构造它

System.Threading.Timer t = System.Threading.Timer    

private void Form1_Load(object sender, EventArgs e)
        {
            // Create the delegate for the Timer type. 
            System.Threading.TimerCallback timeCB = new System.Threading.TimerCallback(d);

            // Establish timer settings. 
              t = new System.Threading.Timer(
              timeCB,     // The TimerCallback delegate object. 
              null,       // Any info to pass into the called method (null for no info). 
              0,          // Amount of time to wait before starting (in milliseconds). 
              1000);      // Interval of time between calls (in milliseconds). 
        }

        void m(object o)
        {
            System.Media.SystemSounds.Hand.Play();
            SReminderEntities ctx = new SReminderEntities();

            var jobs = (from m in ctx.Messages
                        select m).ToList();

            var seljobs = from j in jobs
                          where j.RemindeTime.Date == DateTime.Now.Date
                                && j.RemindeTime.Hour == DateTime.Now.Hour
                                && j.RemindeTime.Minute == DateTime.Now.Minute
                          select j;

            foreach (var j in seljobs)
            {
               // SendGmail("iReminder", j.Text, new string[] { j.User.Email }, "iReminderSender@Gmail.com");
                //this.sendSMS(j.User.Mobile, j.Text);
                System.Media.SystemSounds.Hand.Play();
            }//foreach
        }

---

删除除计时器外的所有代码。将MessageBox添加到勾号处理程序中。它还只开火一次吗？