使用try - catch来处理字母

Question

我写了一个程序来模仿收银机的运作方式.

如果例如用户输入字母而不是数字,我需要一些关于如何使程序处理的帮助.

然后我希望用户输入的字母丢失,用户将获得从头开始的新机会.

我已经使用try和catch为它编写了一些代码,但不确定应该如何编写代码.

class Program
{
    static void Main(string[] args)
    {
        int cash = 0;                    
        double totalAmount = 0;                     
        uint subTotal;                  
        int exchange;                   
        double roundingOffAmount;               

        Console.Write("Please enter a total amount for the cash register    : ");
        totalAmount = double.Parse(Console.ReadLine());

        if (totalAmount < 1)
        {
            Console.BackgroundColor = ConsoleColor.Red;
            Console.WriteLine("\nTotalamount needs to be more\n");
            Console.ResetColor();
            Environment.Exit(0);
        }

        try
        {
            Console.Write("Please enter cash for the cash register: ");
            cash = int.Parse(Console.ReadLine());
            if (cash < totalAmount)
            {
                Console.BackgroundColor = ConsoleColor.Red;
                Console.WriteLine("\nCash needs to be more than totalAmount\n");
                Console.ResetColor();
                Environment.Exit(0);
                Console.WriteLine();
            }
            else
            {
                // Do nothing
            }
        }
        catch (FormatException)
        {
           Console.Write("\nSorry you typed in a letter you need to type in a number");
            Console.WriteLine();
            Console.BackgroundColor = ConsoleColor.Red;
            Console.WriteLine("\nSomething went wrong, please try again");
            Console.ResetColor();
            Console.WriteLine();               
            Main(args);
        }

        subTotal = (uint)Math.Round(totalAmount);
        roundingOffAmount = subTotal - totalAmount;

        exchange = cash - (int)totalAmount;

        Console.WriteLine("\n Receipt"
                        + "\n ------------------------------------"
                        + "\n Totalt \t: \t {0:c}", totalAmount);
        Console.WriteLine(" RoundingOffAmount\t: \t {0:f2}", roundingOffAmount);
        Console.WriteLine(" To pay \t: \t {0:c}", subTotal);
        Console.WriteLine(" Cash \t: \t {0:c}", cash);
        Console.WriteLine(" Exchange \t:\t {0:c}", exchange
                        + "\n ------------------------------------");
        Console.WriteLine();
    }
}

热烈欢迎任何帮助.

Answer 1

首先 - 更重要的是 - 对于货币价值,你应该使用decimal而不是double.十进制浮点数更适合货币值,货币值用十进制精确表示 - 而二进制浮点类型(double和float)更适合"自然"值,如高度和重量,无论如何绝不会有绝对精确的测量值.有关更多详细信息,请参阅有关二进制浮点和十进制浮点的文章.

接下来,我建议您使用decimal.TryParse- 而不是使用异常处理进行此验证,它会返回是否成功.这样你就不必使用try/catch来捕获一个可以轻易避免的非常可预测的异常.例如:

decimal value;
while (!decimal.TryParse(Console.ReadLine(), out value))
{
    Console.WriteLine("Sorry, that wasn't a valid number");
}