//Update, push model
 public void OnUpdatePriceChange(Object sender, PriceChangeEventArgs args)
 {
     if (sender is Subject)			//seul coupling éventuel
         ;							//ok
     int qty = args.qty;
     double price = args.price;
     string str = String.Format("Received qty = {0}, price = {1}", qty, price);
 }
 //notify
 public void ReceivePriceChangeFromFeed(int qty, double price)
 {
     PriceChangeEventArgs args = new PriceChangeEventArgs(qty, price);
     if (priceChanger != null)
         priceChanger(this, args);
 }