C#

class Example4
{
    public static void Test()
    {
        Base4 one = new SubClass4_1();
        Base4 two = new SubClass4_2();
        one.Go();
        two.Go();
        System.Threading.Thread.Sleep(20000); //give the threads time to do stuff before terminating
        one.Stop();
        two.Stop();
    }
}

abstract class Base4
{
    DateTime lastRun = DateTime.UtcNow;
    Timer timer = new Timer();
    public void Go()
    {
        timer.AutoReset = false; //run once (until manually enabled in Again())
        timer.Elapsed += new ElapsedEventHandler(OnElapsedTime);
        timer.Interval = GetInterval();
        timer.Enabled = true;
    }
    public void Stop()
    {
        timer.Close();
        timer.Dispose();
        //nb: code in thread runs to completion even after timer has been disposed of
    }
    private void OnElapsedTime(object source, ElapsedEventArgs e)
    {
        lastRun = DateTime.UtcNow;
        RunSubClassCode();
        Again();
    }

    private void Again()
    {
        //acount for delay caused by the app running
        int interval = GetIntervalAccountForProcessingTime();
        try //stops the "loop" when the timer is disposed of, without exception
        {
            timer.Interval = interval;
            timer.Enabled = true;//kick things off again
        }
        catch (ObjectDisposedException) { }

    }
    private int GetIntervalAccountForProcessingTime()
    {
        int interval = GetInterval();
        interval -= DateTime.UtcNow.Subtract(lastRun).Milliseconds;
        interval = Math.Max(interval, 1);                                   //if we've gone past the period, kick it off straight away
        //while (interval < GetInterval()) interval += GetInterval();       //if we want to wait for the next interval/slot, replace the above line with this code
        return interval;
    }
    protected abstract int GetInterval();
    protected abstract void RunSubClassCode();
}

class SubClass4_1 : Base4
{
    protected override void RunSubClassCode()
    {
        Console.WriteLine("1a" + DateTime.UtcNow.ToString("mm ss ffff"));//easy way to see when things are kicking off
        System.Threading.Thread.Sleep(2000);
        Console.WriteLine("1b");
    }
    protected override int GetInterval()
    {
        return 3000;
    }
}
class SubClass4_2 : Base4
{
    protected override void RunSubClassCode()
    {
        Console.WriteLine("2a" + DateTime.UtcNow.ToString("mm ss ffff"));//easy way to see when things are kicking off
        System.Threading.Thread.Sleep(2000);
        Console.WriteLine("2b");
    }
    protected override int GetInterval()
    {
        return 2000;
    }
}

[assembly: AssemblyVersion("1.2.*.*")]

John Simmons / outlaw programmer wrote:

Does that mean there are now two copies

public IEnumerable<String> GetStrings(){
     foreach(var str in stringList){
         yield return str;
     }
}

"Simplicity carried to the extreme becomes elegance."
-Jon Franklin

public class ListOfThings : List<Thing>{}

public ListOfThings GetListOfThings() { get; set; }

John Simmons / outlaw programmer wrote:

You can do it that way ...