Exactly fire tick event on completion of hour in C

问题:

I want the tick event to fire every hour exactly on completion of the hour. For e.g. it should tick on 8 am then on 9 am then on 10 am etc. It's simple that I need to set the Interval to 3600000.

The problem here is how should I identify when should I start the timer? I'm creating a tool which will run in system tray from the time when user will log on.

回答1:

Please don't create a program that does nothing but waste memory. That's what Windows' Task Scheduler is for. Run your program every hour from such a task.

http://msdn.microsoft.com/en-us/library/aa384006%28v=VS.85%29.aspx

Here's a sample:

• Go to Start->Programs->Accessories->Scheduled Tasks.
• On the right side, click "Add Task..".
• Select your executable.
• Go to the Trigger tab.
• Create Trigger with the following selection:

.

Run Daily 
Start today at 8:00 am
Repeat every 1 Hour

I'm sorry that I can't provide any screenshots since I'm running the german version of Windows 7.

回答2:

May be bellow code is buggy, but the idea is this:

    public void InitTimer()
    {
        DateTime time = DateTime.Now;
        int second = time.Second;
        int minute = time.Minute;
        if (second != 0)
        {
            minute = minute > 0 ? minute-- : 59;
        }

        if (minute == 0 && second == 0)
        {
            // DoAction: in this function also set your timer interval to 3600000
        }
        else
        {
            TimeSpan span = new TimeSpan(0, 60 - minute, 60 - second);
            timer.Interval = (int) span.TotalMilliseconds - 100; 
            timer.Tick += new EventHandler(timer_Tick);
            timer.Start();
        }
    }

    void timer_Tick(object sender, EventArgs e)
    {
        timer.Interval = 3600000;
        // DoAction
    }

Edit: as @smirkingman offered, I removed some millisecond because of latency of project start-up and running of this application: timer.Interval = (int) span.TotalMilliseconds - 100;

回答3:

I think it could be easier if you set up a timer every, let's say, minute, and this timer can check the system clock, when the desired time is less or equal than system time you can just run the actions (in this example with an error of 1 minute maximun)

You can improve it if you make the timer interval dinamyc, for example if you check the time and is still half an hour left you can set the interval for 15 minutes, nex time you reduce it to 5 minutoes and so on until you are checking the clock once a second, for examlpe.

HTH

回答4:

Here's how I did this. The Tick event fires every 20 seconds. Simply change the minutes == "xxx" to whatever time you want the event to fire. If you need events spread out over hours, simply make the interval timer longer. Simple and effective.

private void timer1_Tick(object sender, EventArgs e)
    {
      DateTime Time = DateTime.Now;
          int minutes = Time.Minute;

            if (minutes == 00)  //FIRE ON THE HOUR
                { DO THIS  }

            if (minutes == 15)  //FIRE ON 1/4 HOUR
                {  DO THIS }

            if (minutes == 30)  //FIRE ON 1/2 HOUR
                { DO THIS }

            if (minutes == 45)  //FIRE ON 3/4 HOUR
                { DO THIS }
    }

回答5:

Instead of firing the timer once an hour, maybe it would be more appropriate to fire the timer once a minute, and check to see if it's time yet.

The only problem with this is the worst case lag is 59 seconds. If you need it to fire exactly on the hour (at 10 am sharp), you may need to do some fiddling with the interval the first time so you line up.