变量不会根据输入更改其值

Question

我实际上对编程很新，也许我只是累了，但我在这里找不到问题。 result似乎没有改变它的价值。如您所见，第一个输入为product，第二个输入为city，最后是我们想要的产品的amount。该程序必须打印最终价格（result）。

static void Main(string[] args)
{
    string product = Console.ReadLine().ToLower();
    string city = Console.ReadLine().ToLower();
    double amount = double.Parse(Console.ReadLine());
    double result;
    if (city == "Sofia")
    {
        if (product == "coffee")
        {
            result = amount * 0.50;
            Console.WriteLine(result);

        }
        else if (product == "water")
        {
            result = amount * 0.80;
            Console.WriteLine(result);

        }
        else if (product == "beer")
        {
            result = amount * 1.20;
            Console.WriteLine(result);

        }
        else if (product == "sweets")
        {
            result = amount * 1.45;
            Console.WriteLine(result);

        }
        else if (product == "peanuts")
        {
            result = amount * 1.60;
            Console.WriteLine(result);

        }
    }
    else if (city == "Plovdiv")
    {
        if (product == "coffee")
        {
            result = amount * 0.40;
            Console.WriteLine(result);

        }
        else if (product == "water")
        {
            result = amount * 0.70;
            Console.WriteLine(result);

        }
        else if (product == "beer")
        {
            result = amount * 1.15;
            Console.WriteLine(result);

        }
        else if (product == "sweets")
        {
            result = amount * 1.30;
            Console.WriteLine(result);

        }
        else if (product == "peanuts")
        {
            result = amount * 1.50;
            Console.WriteLine(result);

        }
    }
    else if (city == "Varna")
    {
        if (product == "coffee")
        {
            result = amount * 0.45;
            Console.WriteLine(result);

        }
        else if (product == "water")
        {
            result = amount * 0.70;
            Console.WriteLine(result);

        }
        else if (product == "beer")
        {
            result = amount * 1.10;
            Console.WriteLine(result);

        }
        else if (product == "sweets")
        {
            result = amount * 1.35;
            Console.WriteLine(result);

        }
        else if (product == "peanuts")
        {
            result = amount * 1.55;
            Console.WriteLine(result);

        }
        else
        {
            Console.WriteLine("Invalid");
        }
    }

Answer 1

您将city转换为小写，然后使用大写首字母进行比较！这不会很好。

即。你需要

if (city == "sofia")

等

您可以使用逐行调试器来验证这一点。花一些时间学习如何使用它。调试比能够输入代码更重要。

Answer 2

你能看到代码的精巧程度吗？让我们将实现拆分为模型和业务逻辑（C＃6.0）：

// Dictionary of dictionary; a better solution is to implement a custom class for it 
private static Dictionary<string, Dictionary<string, double>> s_Model = 
  new Dictionary<string, Dictionary<string, double>>(StringComparer.OrdinalIgnoreCase) {
    { "Sofia", new Dictionary<string, double>(StringComparer.OrdinalIgnoreCase) {
      { "coffee", 0.80},
      { "beer", 1.20},
      { "water", 0.50} } },

    { "Plovdiv", new Dictionary<string, double>(StringComparer.OrdinalIgnoreCase) {
      { "coffee", 0.70},
      { "water", 0.45} } },
  };

不仅仅是使用模型;尝试获取所提供的products的{​​{1}};然后为所需的city寻找price：

product

Answer 3

正如Bathsheba所说，你需要将比较改为小写，因为比较是准确的。另外，我建议在最后加Console.ReadKey();，以便在得到结果之前不要关闭。

示例：

    Console.Write("Product: ");
    string product = Console.ReadLine().ToLower();
    Console.Write("City: ");
    string city = Console.ReadLine().ToLower();
    Console.Write("Price: ");
    double amount = Convert.ToDouble(Console.ReadLine());
    double result;
    if (city == "sofia")
    {
        if (product == "coffee")
        {
            result = amount * 0.50;
            Console.WriteLine(result);
        }
    }
    Console.ReadKey();
    }
}

我在运行时将Console.Write();放在那里以便于阅读，所以我可以测试它。

对于许多if，我建议使用switch语句。

例如。

 switch(city)
        {
            case "sofia":
                switch (product)
                {
                    case "coffee":
                        result = amount * 0.50;
                        Console.WriteLine(result);
                        break;
                }
                break;

            case "plovdiv":
                switch (product)
                {
                    case "coffee":
                        result = amount * 0.40;
                        Console.WriteLine(result);
                        break;
                } 
                break;
        }

Answer 4

有人已经看到了小写问题。而且作为你拥有的筑巢的替代品。为了清洁代码，请更改为switch语句以减少嵌套并提高代码的可读性。

 var product = "coffee";
            var city = "VarNa";
            var amount = 10.00;
            double result;

            switch (city.ToLower())
            {
                case "sofia":
                    switch (product)
                    {
                        case "coffee":
                            result = amount * 0.50;
                            Console.WriteLine(result);
                            break;
                        case "water":
                            result = amount * 0.80;
                            Console.WriteLine(result);
                            break;
                        case "beer":
                            result = amount * 1.20;
                            Console.WriteLine(result);
                            break;
                        case "sweets":
                            result = amount * 1.45;
                            Console.WriteLine(result);
                            break;
                        case "peanuts":
                            result = amount * 1.60;
                            Console.WriteLine(result);
                            break;
                    }
                    break;

                case "plovdiv":
                    switch (product)
                    {
                        case "coffee":
                            result = amount * 0.40;
                            Console.WriteLine(result);
                            break;
                        case "water":
                            result = amount * 0.70;
                            Console.WriteLine(result);
                            break;
                        case "beer":
                            result = amount * 1.15;
                            Console.WriteLine(result);
                            break;
                        case "sweets":
                            result = amount * 1.30;
                            Console.WriteLine(result);
                            break;
                        case "peanuts":
                            result = amount * 1.50;
                            Console.WriteLine(result);
                            break;
                    }
                    break;

                case "varna":
                    switch (product)
                    {
                        case "coffee":
                            result = amount * 0.45;
                            Console.WriteLine(result);
                            break;
                        case "water":
                            result = amount * 0.70;
                            Console.WriteLine(result);
                            break;
                        case "beer":
                            result = amount * 1.10;
                            Console.WriteLine(result);
                            break;
                        case "sweets":
                            result = amount * 1.35;
                            Console.WriteLine(result);
                            break;
                        case "peanuts":
                            result = amount * 1.55;
                            Console.WriteLine(result);
                            break;
                        default:
                            Console.WriteLine("Invalid");
                            break;
                    }
                    break;
            }