static void Main(string[] args)
        {
            CDProjectStock stockValue = new CDProjectStock(284.8);
            Caretaker      caretaker  = new Caretaker(stockValue);

            caretaker.Undo();

            caretaker.Save();
            stockValue.SetSharePrice(276.98);

            caretaker.Save();
            stockValue.SetSharePrice(250.02);

            caretaker.Save();
            stockValue.SetSharePrice(299.47);

            caretaker.Undo();
            caretaker.Undo();
        }
 public Caretaker(CDProjectStock stockValue)
 {
     this.StockValue = stockValue;
 }