public void ProccessSmsQueue()
    {
       SmsDbContext context = new SmsDbContext();
       ISmsProvider provider = new ZenviaProvider();
       SmsManager manager = new SmsManager(context, provider);

       try
       {
          manager.ProcessQueue();
       }
       catch (Exception ex)
       {
          EventLog.WriteEntry(ex.Message, EventLogEntryType.Error);
       }
       finally
       {
          context.Dispose();
       }
    }

   protected override void OnStart(string[] args)
   {
      Task.Factory.StartNew(DoWork).ContinueWith( ??? )
   }
}