Windows 服务中的 Timer Elapsed 事件一一

Question

我用 C# 创建了 windows 服务。我使用 timer elapsed 方法对数据库执行一些 CRUD 操作。例如

tmrAPACSEvent = new Timer(10000);
tmrAPACSEvent.Elapsed += new ElapsedEventHandler(tmrAPACSEvent_Elapsed);
tmrAPACSEvent.Enabled = true;

我在 OnStart 方法中创建了这个计时器，事件是

private void tmrAPACSEvent_Elapsed(object sender, ElapsedEventArgs e)
{
    Library.WriteErrorLog("tmrAPACSEvent ticked and some job has been done successfully");

    try
    {
        var UnProcessedEvents = BLCustomService.GetCustomEvents();

        if (UnProcessedEvents != null)
        {
            foreach (EventData eventData in UnProcessedEvents)
            {
                Library.WriteErrorLog(BLCustomService.ChangeEventStatus(eventData).ToString());
                Library.WriteErrorLog(eventData.EventId.ToString());
                var ed = new EventData()
                {
                    dtRealDateTime = eventData.dtRealDateTime,
                    dwCardNumber = eventData.dwCardNumber,
                    strHolderName = eventData.strHolderName,
                    strInitObjName = eventData.strInitObjName
                };

                ed = BLCustomService.AddEvent(ed);
            }
            Library.WriteErrorLog("Events added");
        }
    }
    catch (Exception exception)
    {
        Library.WriteErrorLog("Error 96: " + exception.StackTrace);
    }
}

当我启动服务时，事件并行进行，并且我在数据库中获得了多个对应 "Event" 的数据。我知道运行时间大于定时器运行时间。但是我希望每个线程都必须等待在它之前启动的其他线程完成。

--可能的解决方案-- 我创建全局静态 bool 变量 nad 分配它的真实。在我的事件中将其添加到 if 条件中，然后我将其分配为 false 直到 foreach 循环结束。

  private static bool adminForElapsedEvent = true;
    private void tmrAPACSEvent_Elapsed(object sender, ElapsedEventArgs e)
    {
        Library.WriteErrorLog("tmrAPACSEvent ticked and some job has been done successfully");

        try
        {
            var UnProcessedEvents = BLCustomService.GetCustomEvents();

            //Library.WriteErrorLog("tmrAPACSEvent ticked and some job has been done successfully" + UnProcessedEvents.Count);
            if (UnProcessedEvents != null || adminForElapsedEvent)
            {
                adminForElapsedEvent = false;

                // doing some wordks
                adminForElapsedEvent = true;
            }
        }
        catch (Exception exception)
        {
            Library.WriteErrorLog("Error 96: " + exception.StackTrace);
        }
    }

此方法第一次有效，但几分钟后 Elapse 事件再次运行，并重复插入。

Answer 1

您可以尝试的第一件事：设置 tmrAPACSEvent.Enabled = false 而不是 adminForElapsedEvent = false;。那么你甚至不需要全局变量。

这不是 fool-proof，因为您运行处于竞争状态。所以下一个建议是锁定你的代码。但是不要使用普通锁，使用 Mutex 我发现它可以提供更好的资源访问控制。所以你的代码现在看起来像这样：

// Create a new Mutex. The creating thread does not own the mutex.
private static Mutex mux = new Mutex();

private void tmrAPACSEvent_Elapsed(object sender, ElapsedEventArgs e)
{
    Library.WriteErrorLog("tmrAPACSEvent ticked and some job has been done successfully");

    try
    {
        var UnProcessedEvents = BLCustomService.GetCustomEvents();

        if (UnProcessedEvents != null)
        {
            tmrAPACSEvent.Enabled = false;

            // Wait until it is safe to enter, and do not enter if the request times out.
            if (mux.WaitOne(7000))
            {
                // do work

                // note this is inside the mutex so that the timer is guaranteed enabled, even for just a moment
                tmrAPACSEvent.Enabled = true;
            }
        }
    }
    catch (Exception exception)
    {
        Library.WriteErrorLog("Error 96: " + exception.StackTrace);
    }
}

Windows 服务中的 Timer Elapsed 事件一一

Timer Elapsed event one by one in Windows Service

c#

events

multithreading

windows-services

timer