class AuditManager
{
      //set of methods

      int AuditEvent(int x){
          Event event=new Event(x);
          event.SaveToDB();
       }
}

class Event
{
    //set of methods
    User getUserOfEvent(int eventId){
        User usr = Respository.Get(eventId);
        Audit.Singleton.AuditEvent(usr.x); //circular dependency between Audir and event
        return usr;
    }

    int SaveToDB()
   {
      Db.Singleton.Save(this);
   }

}