C#运算运算的错误处理

Question

我想用 C# 创建一个控制台计算器。从名为 expressions.txt 的文件中读取数据。文件的列由两个数字和一个操作组成。我只想使用文件中的操作符号和我选择的数字进行计算。如果我停止输入，它将停止迭代，然后退出程序。我也想做错误处理。例如：如果列表中没有运算符，我想得到一个“错误的运算符”消息。如果我想除以 0，或者如果我输入字符串而不是数字，我想得到“其他错误”消息。我在错误处理中做错了什么。我想寻求有关正确错误处理的帮助。这是我的代码：

class Program
{

    // 1.Reading:
    static List<Expression> expressions = new List<Expression>();

    static void Read()
    {
        string[] rows = File.ReadAllLines("expressions.txt");
        foreach (var item in rows)
        {
            expressions.Add(new Expression(item));
        }

    }


    //counting:
    static void Calculator()
    {
        //string[] operators = { "div", "mod", "%", "/", "*", "-", "+" };
        string counting = "";
        string actionRequest = "";
        while (actionRequest != "stop")
        {
            Console.Write("\nI need an action:");
            actionRequest = Console.ReadLine();
            if (actionRequest != "stop")
            {
                string[] data = actionRequest.Split(' ');
                int firstNumber = int.Parse(data[0]);
                string symbol = Convert.ToString(data[1]);
                int secondNumber = int.Parse(data[2]);

                try
                {
                    counting = firstNumber + " " + symbol + " " + secondNumber;
                    switch (symbol)
                    {
                        case "mod":
                            actionRequest = counting + " = " + (firstNumber % secondNumber);
                            Console.WriteLine($"{counting} = {firstNumber % secondNumber}");
                            break;
                        case "div":
                            actionRequest = counting + " = " + (firstNumber / secondNumber);
                            Console.WriteLine($"{counting} = {firstNumber / secondNumber}");
                            break;
                        case "/":
                            actionRequest = counting + " = " + (Double.Parse(data[0]) / Double.Parse(data[2]));
                            Console.WriteLine($"{counting} = {Double.Parse(data[0]) / Double.Parse(data[2])}");
                            break;
                        case "*":
                            actionRequest = counting + " = " + (firstNumber * secondNumber);
                            Console.WriteLine($"{counting} = {firstNumber * secondNumber}");
                            break;
                        case "+":
                            actionRequest = counting + " = " + (firstNumber + secondNumber);
                            Console.WriteLine($"{counting} = {firstNumber + secondNumber}");
                            break;
                        case "-":
                            actionRequest = counting + " = " + (firstNumber - secondNumber);
                            Console.WriteLine($"{counting} = {firstNumber - secondNumber}");
                            break;
                        //default:          // --> that's the fault.
                        //    return ($"Bad operator!");
                    }
                }

                catch (Exception)
                {
                    Console.WriteLine($"Other error!");
                }



            }
            else
            {
                Console.Write("Exit ---> |press any key|");
                break;

            }



        }

    }

    static void Main(string[] args)
    {
        Read();
        Calculator();
        Console.ReadKey();
    }

}

Expression.cs:

class Expression
{

    public int op1, op2;
    public string operation;

    // ctor
    public Expression(string row)
    {
        op1 = Convert.ToInt32(row.Split()[0]);
        operation = row.Split()[1];
        op2 = Convert.ToInt32(row.Split()[2]);
    }

}

这是练习的expressions.txt：

Answer 1

让我们先提取模型（所有可能的操作）：

static Dictionary<string, Func<double, double, double>> s_Operations = new
  Dictionary<string, Func<double, double, double>>(StringComparer.OrdinalIgnoreCase) {
    {"+",   (a, b) => a + b},
    {"-",   (a, b) => a - b},
    {"*",   (a, b) => a * b},
    {"/",   (a, b) => a / b},
    {"%",   (a, b) => a % b},
    {"div", (a, b) => a / b - a % b}, // integer division
    {"mod", (a, b) => a % b},  
    // Add more operations if required, e.g. "pow"      
  };

继续提取：我们准备实施Compute：

   static string Compute(string line) {
     if (line == null)
       return "null";

     // The simplest; spaces are mandatory: 
     // "3 + 4" is valid, when "3 +4", "3+ 4", "3+4" are not
     string[] items = line.Split(' ', StringSplitOptions.RemoveEmptyEntries);

     // if we have exactly three items: double, func, double
     // we can compute the formula
     if (items.Length == 3 &&
         double.TryParse(items[0], out var a) &&
         s_Operations.TryGetValue(items[1], out var func) &&
         double.TryParse(items[2], out var b)) 
       return $"{string.Join(" ", items)} = {func(a, b)}";
     else
       return "Syntax error";
   }

然后我们就可以轻松处理文件了...

   static void Calulator() {
     foreach (var line in File.ReadLines(@"c:\myFile.txt")) {
       if (line.Trim() == "stop")
         break;

       Console.WriteLine(Compute(line));    
     }
   }

请注意，在这种情况下，唯一可能的错误是 number / 0 即 +Inf 或 -Inf 和 0 / 0 即 NaN（Not a N数).

...或执行控制台输入：

   static void Calulator() {
     while (true) {
       Console.Write("\nI need an action:");

       string actionRequest = Console.ReadLine().Trim();

       if (actionRequest == "stop")
         break;

       Console.WriteLine(Compute(actionRequest));    
     }
   }

C#运算运算的错误处理

Error handling of operation calculations with C#

.net

c#

console-application

txt