C# Timers stopping intermittently

Can anybody suggest any reasons why a C# timer (created in a code-behind class) would stop without being told to?

My timer starts on page load and then stops when I click a button. I don't need to click the button for it to sometimes stop. IIS is not being restarted to my knowledge and no errors are being thrown either.

This is confusing me quite a bit...

Thanks.

    // This gets called on page_load
    private void checkTimer()
    {
        if (!parentTimer.Enabled) // If parent timer is not enabled then it is probably the start of a new day (after a night time server backup which kills timers)
        {
            parentTimer.Interval = 60000; // One minute
            parentTimer.Elapsed += new ElapsedEventHandler(parentTimer_Elapsed); // Define what happens when elapsed
            parentTimer.AutoReset = true; // Set timer to repeat
            parentTimer.Enabled = true; // Start the timer
        }
    }

    protected void btnCancel_Click(object sender, System.EventArgs e)
    {
        parentTimer.Stop();
 开发者_如何学编程       ...etc...
    }

Note: I do not change ParentTimer at all in its elapsed method.

Basically ParentTimer governs a list of ChildTimers. If ParentTimer elapses it checks if one or more of the ChildTimers have elapsed too, if so, there is an event, if not then it resets the ChildTimer and carries on.

My suspicion is it's because the worker process for the page is stopping at the end of the request.

You could try increasing the request time out, but a better question is Can you explain why you're trying to do this ? What is the problem you're trying to solve ?

Remember, that regardless of all the fluff that ASP.Net puts around your code to make you feel comfortable (session state, viewstate etc), a web request is stateless and should be considered as a distinct pass of logic, it's not like a windows application where a background thread of code in your void Main(...) function is constantly running.

A timer is tied to the thread that created it and in the case of ASP.net the thread that handles each page request issued by a given user will change frequently due to the use of worker threads and the thread pool.

Using a timer at page-level simply won't work; you need to be tracking the state at Session-level (tied to the particular user) as your starting point.

In fact, I just wouldn't use timers at all in a web application, because their execution is simply not guaranteed.

If you're using this to run a background task - consider firing up your own worker thread in Application_Start or something like that. The thread will be terminated when the app pool recycles. You should also look at manually shutting the thread down the application is being shut down too.

Be careful with this, however, this thread can't assume it's always the only one running - due to IIS overlapped recycling, when a new one fires up the old one could still be running in the old AppDomain.