protected virtual void OnPriceChanged(PriceChangedEventArgs e)
 {
     if (PriceChanged != null)
     {
         PriceChanged(this, e);
     }
 }
 private static void Stock_PriceChanged1(object sender, PriceChangedEventArgs e)
 {
     Console.WriteLine("MSFT: {0} {1}", e.LastPrice, e.NewPrice);
 }