Question

In my c# windows service i’m starting several threads. Each thread should dispose it’s objects after a specific period of time with no activity.

I tried the System.Threading.Timer and System.Timers.Timer classes but they all raise the events on a different thread.

This is what’s happining:

• create several threads during service.start
• each thread monitors a directory and activates a resource extensive function for every new file
• After a 1 hour of no activity inside the thread (no files are handled during that period) i want to cleanup the resources inside that thread (structuremap, threadlocal classes)

Answer 1

Assuming that by “a period of no activity” you mean a thread that has been in the WaitSleepJoin for too long, you can interrupt such a thread by calling its Interrupt Method:

var t = new Thread(WorkerThred);
t.Start();

// when the thread's been inactive for too long, kill it!
t.Interrupt();

This will cause a ThreadInterruptedException to be thrown in the target thread. Hence, you can catch the exception in order to dispose the thread’s resources:

private void WorkerThred()
{
    try
    {
        DoWork();
    }
    catch (ThreadInterruptedException)
    {
        DisposeResources();
    }
}

Now you need some way of tracking the amount of time each thread stays inactive. For instance, create a method that all threads must call before going to sleep or waiting on a mutex:

public static void UpdateLastActiveTime()
{
    var t = Thread.CurrentThread;
    if (!lastActiveTime.ContainsKey(t))
        lastActiveTime.Add(t, DateTime.Now);
    else
        lastActiveTime[t] = DateTime.Now;
}

private static Dictionary<Thread, DateTime> lastActiveTime;

Finally, to check for how long a specific thread has been inactive, call the following method:

public static TimeSpan GetInactiveTime(Thread t)
{
    // if thread isn't sleeping anymore update its time
    if (t.ThreadState != ThreadState.WaitSleepJoin)
        lastActiveTime[t] = DateTime.Now;
    return DateTime.Now - lastActiveTime[t];
}

I believe that using this pattern you will be able to create a thread manager class that meets your requirements.