I wonder if anyone can help me understand something. I have a service running every 30 seconds via a system.timers.timer. This will execute a procedure which will check our database and process some data if there is any. If it does need to process data then there can be loads of different things it needs to do, as a result a parallel.for is used (as we want each iteration to be a separate task/thread) However each iteration can take a while so we spawn another task which creates another system.timers.timer to use so we can log something every 5 seconds. Once this specific task is completed we want to stop the timer.

This is where I am having an issue. If the parallel.for has multiple iterations then the timer stops and releases the object. However when the next task finishes it falls over when trying to stop the timer, I assume because the timer object is null so it wont finish all its jobs. How do I get around this. Below is a simple version of what I have done if someone could explain to me what is actually happening with the timer in the example below it is timer1..

private void timer_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
{
    RunProcess();
}

private void RunProcess()
{
    //Go To Database to figure out what data we need to get
    Dataresult // This is the data result from the previous query
    ParallelOptions options = new ParallelOptions()
    {
      CancellationToken = cancellationToken.Token,
      MaxDegreeOfParallelism = 10  
    };
    ParallelLoopResult result = Parallel.For(0, DataResult.Rows.Count, options, async i =>
    {
       CancellationTokenSource ctForTimer = new CancellationTokenSource();
       CancellationToken ct = ctTimer.Token;
       int ID = DataResult.rows[i]["ID"]
       Task setTimer = Task.Factory.StartNew(() => StartTimer(ID, ct));
       // DO STUFF - so go off to get data and work with it
       ctForTimer.Cancel();
    }
}

public void StartTimer(int id, CancellationToken ct)
{
    timer1 = new System.Timers.Timer(10000);  // 1000 milliseconds = 1 seconds
    timer1.AutoReset = true;
    timer1.Elapsed += (sender, e) => { timer1_Elapsed(id, ct); };
    timer1.Start();
}

 private void timer1_Elapsed(int id, CancellationToken ct)
 {
     if (ct.IsCancellationRequested)
     {
         EndTimer1();
         // DO OTher stuff
     }
     else
     {
         // DO Stuff here like update the time in the db
     }            
 }

 public void EndTimer1()
 {
     timer1.Stop();
     timer1 = null;
 }

So my problem is if I have say 2 or 3 iterations of the loop then the timer1 has already stopped and cleared down, so for iteration 2 and 3 it falls over when trying to End the timer1.