public static void Test()
        {
            IFactory factory = new UndergraduateFactory();
            LeiFeng  student = factory.CreateLeiFeng();

            student.BuyRice();
            student.Sweep();
            student.Wash();
        }
        public static void Test()
        {
            LeiFeng studentA = SimpleFactory.CreateLeiFeng("Undergraduate");

            studentA.BuyRice();

            LeiFeng studentB = SimpleFactory.CreateLeiFeng("Undergraduate");

            studentB.Sweep();

            LeiFeng studentC = SimpleFactory.CreateLeiFeng("Undergraduate");

            studentC.Wash();
        }
        public static LeiFeng CreateLeiFeng(string type)
        {
            LeiFeng result = null;

            switch (type)
            {
            case "Volunteer":
                result = new Volunteer();
                break;

            case "Undergraduate":
                result = new Undergraduate();
                break;

            default:
                break;
            }
            return(result);
        }