void IObserver <TradeNotification> .OnNext(TradeNotification tradeNotification)
 {
     if (tradeNotification.isSuccessful)
     {
         OnItemBought(tradeNotification.tradedObject, tradeNotification.seller);
     }
 }
        //------------------------Observable<TradeNotification>----------------------------

        protected void NotifyTradeObservers(TradeNotification notification)
        {
            for (int i = 0; i < tradeObservers.Count; i++)
            {
                tradeObservers[i].OnNext(notification);
            }
        }