c# - 在 C# 中无限循环

Question

我是 c# 的新手，我遇到了一个不会中断的 while 循环的问题。它只是一个简单的控制台计算器，我希望 switch 语句在输入正确时跳出循环，否则继续循环。问题是即使选择了正确的字母它也会一直循环，例如 A 表示添加，这是我的代码:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace basic_calc
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("this is a basic calculator");
            double num1 = Getvalue("Enter the first number: ");
            double num2 = Getvalue("Enter the second number: ");

            double output = 0;
            while (true)
            {
                Console.WriteLine(" Please select an operation (A)dd, (S)ubtract, (M)ultiply, (D)ivide");
                char operation = Console.ReadKey().KeyChar;
                operation = Char.ToUpper(operation);
                switch (operation)
                {
                    case 'A':
                        output = Add(num1, num2);
                        break;
                    case 'S':
                        output = Subtract(num1, num2);
                        break;
                    case 'M':
                        output = Multiply(num1, num2);
                        break;
                    case 'D':
                        output = Divide(num1, num2);
                        break;
                    default:
                        Console.ForegroundColor = ConsoleColor.Red;
                        Console.WriteLine("INVALID INPUT!!!!!!!!!!!!!!!");
                        Console.ResetColor();
                        continue;
                }    
            }


            Console.WriteLine("\nresult: "+ output);

            Console.ReadKey();
        }
        private static double Getvalue(string input)
        {
            //the value to be returned
            double value;
            while (true)
            {
                Console.Write(input);
                string number = Console.ReadLine();
                if (double.TryParse(number, out value))
                {
                    return value;

                }
                else
                    Console.WriteLine("please enter a number for this calculator");
            }
        }
        private static double Add(double n1, double n2){return n1 + n2;}
        private static double Subtract(double n1, double n2) { return n1 - n2; }
        private static double Multiply(double n1, double n2) { return n1 * n2; }
        private static double Divide(double n1, double n2) { return n1 / n2; }
    }
}

Answer 1

只需在开关之后添加一个break即可:

switch (operation)
{
    case 'A':
        output = Add(num1, num2);
        break;
    case 'S':
        output = Subtract(num1, num2);
        break;
    case 'M':
        output = Multiply(num1, num2);
        break;
    case 'D':
        output = Divide(num1, num2);
        break;
    default:
        Console.ForegroundColor = ConsoleColor.Red;
        Console.WriteLine("INVALID INPUT!!!!!!!!!!!!!!!");
        Console.ResetColor();
        continue;
}
break; // This will exit the loop when a match is found.

如果未找到匹配项，您将使用 continue，如果找到匹配项，switch 之后的 break 将退出循环.