static void Main(string[] args)
        {
            File.WriteAllText(AppDomain.CurrentDomain.BaseDirectory + @"\" + "output.txt", "");

             Stock stock1 = new Stock("Technology", 160, 5, 15);
             Stock stock2 = new Stock("Retail", 30, 2, 6);
             Stock stock3 = new Stock("Banking", 90, 4, 10);
             Stock stock4 = new Stock("Commodity", 500, 20, 50);

             StockBroker b1 = new StockBroker("Broker 1");
             b1.AddStock(stock1);
             b1.AddStock(stock2);

             StockBroker b2 = new StockBroker("Broker 2");
             b2.AddStock(stock1);
             b2.AddStock(stock3);
             b2.AddStock(stock4);

             StockBroker b3 = new StockBroker("Broker 3");
             b3.AddStock(stock1);
             b3.AddStock(stock3);

             StockBroker b4 = new StockBroker("Broker 4");
             b4.AddStock(stock1);
             b4.AddStock(stock2);
             b4.AddStock(stock3);
             b4.AddStock(stock4);

             System.Threading.Thread.Sleep(2000);
             stock1.KillThread();
             stock2.KillThread();
             stock3.KillThread();
             stock4.KillThread();
        }
 //add a stock into this broker's stockList
 //and invoke CustomEvent
 public void AddStock(Stock newStock)
 {
     stockList.Add(newStock);
      newStock.StockEvent += CustomEvent;
 }