Question

我在我的上一个while循环中获得了无限循环，状态如下：while（Valid3 == false）... 我希望收到console.writeline（“无效输入，请重试”），直到用户满足参数为止，但是当我输入无效输入时，我会收到无限循环。虽然我觉得这里使用的逻辑与先前使用的循环中的逻辑相同。下面是我的所有代码。

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

namespace CalculatorApp
{
class Program
{
    static void Main(string[] args)
    {
        // Declare my and then initialize to zero.
        float num1 = 0; float num2 = 0;

        // Display title as the C# console calculator app.

        Console.WriteLine("Console Calculator in C#\r");
        Console.WriteLine("------------------------\n");

        // Ask the user to type the first number.
        //Console.WriteLine("Type a number, and then press Enter");


        Console.WriteLine("Type a number, and then press Enter");

        List<string> validChars = new List<string>() { "a", "s", "d", "m"};
        double negSqrt = Math.Sqrt(-1);
        bool Valid = false;
        bool Valid2 = false;
        bool Valid3 = false;
        float Number;
        while (Valid == false)
        {
            string Input = Console.ReadLine();
            if (!float.TryParse(Input, out Number))
            {
                Console.WriteLine("Not an integer, please try again.");
            }
            else
            {
                Valid = true;
                num1 = (float)Convert.ToDecimal(Input);
            }
        }

        // Ask the user to type the second number.
        Console.WriteLine("Type another number, and then press Enter");
        while (Valid2 == false)
        {
            string Input2 = Console.ReadLine();
            if (!float.TryParse(Input2, out Number))
            {
                Console.WriteLine("Not an integer, please try again.");

            }
            else
            {
                Valid2 = true;
                num2 = (float)Convert.ToDecimal(Input2);
            }
        }

        // Ask the user to choose an option.
        Console.WriteLine("Choose an option from the following list:");
        Console.WriteLine("\ta - Add");
        Console.WriteLine("\ts - Subtract");
        Console.WriteLine("\tm - Multiply");
        Console.WriteLine("\td - Divide");
        Console.Write("Your option? ");
        string o = Console.ReadLine();
        while (Valid3 == false)
        {
            foreach (string s in validChars)
            {
                if (!o.Contains(s))
                {
                    Console.WriteLine("Invalid input please try again");
                }
                else
                {
                    Valid3 = true;
                    switch (o)
                    {
                        case "a":
                            Console.WriteLine($"Your result: {num1} + {num2} = " + (num1 + num2));
                            break;
                        case "s":
                            Console.WriteLine($"Your result: {num1} - {num2} = " + (num1 - num2));
                            break;
                        case "m":
                            Console.WriteLine($"Your result: {num1} * {num2} = " + (num1 * num2));
                            break;
                        case "d":
                            Console.WriteLine($"Your result: {num1} / {num2} = " + (num1 / num2));
                            break;

                    }
                }
            }
        }
            // Use a switch statement to do the math.

            // Wait for the user to respond before closing.
            Console.Write("Press any key to close the Calculator console app...");
            Console.ReadKey();
        }
    }
}

Answer 1

在您的while循环内移动Console.ReadLine()

    while (Valid3) {
        string o = Console.ReadLine();
...

为什么会进行无限循环

您要输入，输入后，进入while循环。如果输入无效，则不再需要其他输入，而是一次又一次地遍历同一输入。

Answer 2

您必须在循环内读取运算符，否则，您将始终反复比较相同的无效输入。另外，您可以简化测试。无需对有效输入列表进行测试，只需在switch语句中添加默认大小写即可。如果没有其他情况匹配，它将被执行。

bool isOperatorValid;
do {
    isOperatorValid = true;
    switch (Console.ReadLine()) {
        case "a":
            Console.WriteLine($"Your result: {num1} + {num2} = " + (num1 + num2));
            break;
        case "s":
            Console.WriteLine($"Your result: {num1} - {num2} = " + (num1 - num2));
            break;
        case "m":
            Console.WriteLine($"Your result: {num1} * {num2} = " + (num1 * num2));
            break;
        case "d":
            Console.WriteLine($"Your result: {num1} / {num2} = " + (num1 / num2));
            break;
        default:
            Console.WriteLine("Invalid input please try again");
            isOperatorValid = false;
            break;
    }
} while (!isOperatorValid);

isOperatorValid比Valid3更清晰。我还使用了一条do-while语句，能够在循环结束时测试条件，因为开始循环时我们不知道其结果。

在C＃中陷入无限循环-计算器应用初学者

2 个答案: