C# 从用户输入中获取类名

Question

在 C# 中，如何使用用户输入或流来决定使用哪个类？此示例使用Console.Readline()，但实际程序将根据循环中读取的流中的数据来决定使用哪个类。这只是简化了问题的一个例子：

static void Main(string[] args)
        {
            stock aapl = new stock(); //instantiate a class for Apple Stock
            stock fb = new stock();   //instantiate a class for Facebook Stock

            Console.WriteLine("Please enter a symbol for Apple or Facebook");
            string symbol = Console.ReadLine(); //this should get the class to work on

            Console.WriteLine("Please enter yesterdays price for the symbol");
            double yestPrice = Convert.ToDouble(Console.ReadLine());

            Console.WriteLine("Please enter Todays Price for the symbol");
            double currPrice = Convert.ToDouble(Console.ReadLine());

            //Assuming aapl was entered, how do I
            //set values for the appl member using
            //the symbol variable like this:
            symbol.YesterdaysPrice = yestPrice; 
            symbol.CurrentPrice = currPrice; 

        }
        class stock
        {
            private double yesterdayPrice;
            private double currentPrice;
            private double dailyGain;

            public double YesterdaysPrice
            {
                get { return yesterdayPrice; }
                set { yesterdayPrice = value; }
            }
            public double CurrentPrice
            {
                get { return currentPrice; }
                set { currentPrice = value; }
            }
            public double DailyGain
            {
                get { return currentPrice - yesterdayPrice; }
                // No need to ever set directly
            }
        }

Answer 1

下面是一个使用字典来解决这个问题的例子：

    static void Main(string[] args)
    {
        Dictionary<string, stock> stocks = new Dictionary<string, stock>(StringComparer.CurrentCultureIgnoreCase);

        //Add the initial stocks here if desired.

        Console.WriteLine("Please enter a symbol");
        string symbol = Console.ReadLine();

        Console.WriteLine("Please enter yesterdays price for the symbol");
        double yestPrice = Convert.ToDouble(Console.ReadLine());

        Console.WriteLine("Please enter Todays Price for the symbol");
        double currPrice = Convert.ToDouble(Console.ReadLine());

        if (stocks.ContainsKey(symbol))     //The dictionary contains the stock
        {
            stocks[symbol].YesterdaysPrice = yestPrice;
            stocks[symbol].CurrentPrice = currPrice;
        }
        else
        {
            //The stock wasn't found, we can either say invalid stock, or add one like this:
            stocks[symbol] = new stock()
            {
                YesterdaysPrice = yestPrice,
                CurrentPrice = currPrice;
            };
        }
    }

字典在顶部声明，将保存所有输入的符号。用户输入代码和数据后，if 语句检查是否已经存在具有该代码的股票，如果存在，则更新其值。快速说明一下，我创建了带有参数StringComparer.CurrentCultureIgnoreCase 的字典，以便用户可以输入 AAPL 或 aapl 或 aApL 并且它们都将匹配相同的股票，默认情况下它区分大小写并会为这些股票创建不同的股票.

如果库存不存在，您可以告诉用户它是无效库存，或者您可以添加库存，因为您拥有执行此操作所需的所有数据。我展示了使用价格属性的内联初始化程序添加新股票的示例。

Answer 2

Ron 建议这样做

        static readonly IDictionary<string, Stock> Stocks = new Dictionary<string, Stock>();
        static void Main(string[] args)
        {

            Console.WriteLine("Please enter a symbol for Apple or Facebook");
            var symbol = Console.ReadLine(); //this should get the class to work on

            Console.WriteLine("Please enter yesterdays price for the symbol");
            var yestPrice = Convert.ToDouble(Console.ReadLine());

            Console.WriteLine("Please enter Todays Price for the symbol");
            var currPrice = Convert.ToDouble(Console.ReadLine());


            Stock stock;
            if (Stocks.ContainsKey(symbol))
                stock = Stocks[symbol];
            else
            {
                stock=new Stock();
                Stocks[symbol] = stock;
            }


            stock.YesterdaysPrice = yestPrice;
            stock.CurrentPrice = currPrice;

        }