Servicing the first timer

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C#

C#4.0

I have started two threading.timers which has callback like this called on expiry:

private void N_ArTimeoutExpired(object state)
       {
           // Timeout raised. Set timeout error state
           String message = string.Empty;
           message = "N_Ar Timer Expired at -> " + DateTime.Now.ToString("h:mm:ss.fff");
           _logger.Info(message);
           Iso15765Transport.ErrorEventArgs errorEventArgs = new Iso15765Transport.ErrorEventArgs("N_Ar timer expired");
           _owner.SetEvent(errorEventArgs);

       }

Here on expiry it raises an event which calls following method:

public void OnTimeOut(object o, ErrorEventArgs e)
       {
           lock (_locker)
           {
             
             
               string errorMsg = e._errorMsg;
               PublishErrorFrame(errorMsg);
               ResetAllTimers();
               ResetStateMachine();
               AbortCurrentReception();
             
           }

       }

My problem is that in this method i have to service the first timer that expires and reject the other one.How can i do that?

Considering a situation where both timers expires simultaneously.
I cant put a flag and simply check in that way. Reason is that when first timer expires , i reset all state machines and communication is started again. The chances are that i have a timer that expired earlier before resetting state machines.