DateTime now = DateTime.Now;
                DateTime dateAsta = asta.DataScadenza.
                    AddHours(Convert.ToDouble(asta.OraScadenza.Split(",".ToCharArray())[0])).
                    AddMinutes(Convert.ToDouble(asta.OraScadenza.Split(",".ToCharArray())[1]));
TimeSpan duration = dateAsta.Subtract(now).Duration();
System.Timers.Timer timer = new System.Timers.Timer(duration.TotalMilliseconds);
                    asta.TimerHashCode = timer.GetHashCode();
timer.Elapsed += new System.Timers.ElapsedEventHandler(timer_Elapsed);
                    timer.AutoReset = false;
                    timer.Enabled = true;
                    GC.KeepAlive(timer);

void timer_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
        {
            try
            {
                using (MioContext context = new MioContext())
                {
                    int hc = sender.GetHashCode();
                    Asta asta = context.AstaSet.SingleOrDefault(x => x.TimerHashCode == hc);
                 .......
                }
            }
            catch (Exception ex)
            {
                LoggerWrapper.Write("AstaManager.timer_Elapsed", ex, NLog.LogLevel.Error);
            }
        }

public sealed class AlarmsManager:IDisposable
    {
        //Intervallo lettura default 1min
        int interval = 60000;
        Timer timer = null;
        private static Dictionary<int, DateTime> inCorsoItems = null;
        private static Dictionary<int, DateTime> chiusiItems = null;
        static readonly AlarmsManager _instance = new AlarmsManager();
        public static AlarmsManager Instance
        {
            get
            {
                return _instance;
            }
        }
        private AlarmsManager()
        {
            if (ConfigurationManager.AppSettings["AlarmsManagerInterval"] != null)
                interval = Convert.ToInt32(ConfigurationManager.AppSettings["AlarmsManagerInterval"]);
            inCorsoItems = new Dictionary<int, DateTime>();
            chiusiItems = new Dictionary<int, DateTime>();
            if (!IsConfiguredFromXml())
                Start();
        }
        public void AddNewInCorso(int astaID, DateTime scadenza)
        {
            inCorsoItems.Add(astaID, scadenza);
        }
        private void Start()
        {
            timer = new Timer(interval);
            timer.Elapsed += new ElapsedEventHandler(timer_Elapsed);
            timer.Enabled = true;
        }
        public void StopAndWriteObserved()
        {
            //Scrivo su un file xml tutte le aste in sospeso
            //mi serve in caso Application_Stop
        }
        public bool IsConfiguredFromXml()
        {
            //Leggo il file xml e reimposto tutte le scadenza
            //se trovo aste scadute Update
            //Problema potrebbe passare troppo tempo e la chiusura avverrebbe con un ritardo
            return false;
        }
        void timer_Elapsed(object sender, ElapsedEventArgs e)
        {
            var changedList = from item in inCorsoItems
                              where item.Value <= DateTime.Now
                              select item;
            var daCancellare = from todel in chiusiItems
                               where todel.Value <= DateTime.Now
                               select todel;
            foreach (var item in changedList)
            {
                AstaManager astaManager = new AstaManager();
                astaManager.UpdateStato(item.Key);
                chiusiItems.Add(item.Key, DateTime.Now.AddDays(1));
                inCorsoItems.Remove(item.Key);
            }
            foreach (var todel in daCancellare)
            {
                AstaManager astaManager = new AstaManager();
                astaManager.CancellaAsta(todel.Key);
                chiusiItems.Remove(todel.Key);
            }
        }

        #region IDisposable Membri di

        public void Dispose()
        {
            StopAndWriteObserved();
        }

        #endregion
    }