private static void GetNextCallTimerOnElapsed(object sender, ElapsedEventArgs elapsedEventArgs) { var request = MockAPI.getNextCallRequest(); if (request != null) { // when the request of the room is cancelled if (request.WakeUpTime == null) { RemoveFromSortedWakeUpList(request); } // when the request of the room is not cancelled else { RemoveFromSortedWakeUpList(request); InsertIntoSortedWakeUpList(request); } } Alarm(); }