Question

我无法弄清楚我做错了什么。我想要做的是获取用户输入并验证它是一个数字，在1-4之间，没有其他任何事情崩溃该程序。但我不能让tryparse数字验证工作。它不会运行里面的代码。 1和5之外的任何整数都不会抛出错误，但输入小数，字符串等。这是一个明显的解决方案，但我似乎无法弄明白。

class Program
{
    static void Main(string[] args)
    {

        string[] ColorsArray = new string[12] { "blue", "red", "green", "yellow", "blue", "green", "blue", "yellow", "red", "green", "red", "yellow" };


        float[] LengthArray = new float[12] { 1.3f, 1.4f, 5.6f, 1.5f, 3.5f, 5.4f, 1.2f, 6.5f, 4.4f, 4.1f, 3.3f, 4.9f };




            Console.WriteLine("Select a color of Fish by entering the corresponding number \r\n 1. Blue \r\n 2. Yellow \r\n 3. Red \r\n 4. Green");
            string ColorChoiceNumber = Console.ReadLine();

            int ColorChoiceNumberInt = int.Parse(ColorChoiceNumber);




            if (ColorChoiceNumberInt == 1)
            {
                Console.WriteLine("The Biggest Blue Fish is Fish Number ");

            }
           else if (ColorChoiceNumberInt == 2)
            {
                Console.WriteLine("The Biggest Yellow Fish is Fish Number");
            }
           else if (ColorChoiceNumberInt == 3)
            {
                Console.WriteLine("The Biggest Red Fish is Fish Number");
            }
            else if (ColorChoiceNumberInt == 4)
            {
                Console.WriteLine("The Biggest Green Fish is Fish Number");
            }

            else if (!(int.TryParse(ColorChoiceNumber, out ColorChoiceNumberInt)) && ColorChoiceNumberInt < 1 && ColorChoiceNumberInt > 4)
            {

                Console.WriteLine("Please only enter a number. It must be 1-4.");
                ColorChoiceNumber = Console.ReadLine();
                int.TryParse(ColorChoiceNumber, out ColorChoiceNumberInt);



            }
            else
        {
            Console.WriteLine("Please only enter a number. It must be 1-4.");
            ColorChoiceNumber = Console.ReadLine();
            int.TryParse(ColorChoiceNumber, out ColorChoiceNumberInt);
        }



        }




    }

}

Answer 1

我开始回答，但发现你的代码存在很多问题，因此重构似乎更容易，让你通过阅读工作答案来学习。

试试这个：

string[] ColorsArray = new string[12] { "blue", "red", "green", "yellow", "blue", "green", "blue", "yellow", "red", "green", "red", "yellow" };
float[] LengthArray = new float[12] { 1.3f, 1.4f, 5.6f, 1.5f, 3.5f, 5.4f, 1.2f, 6.5f, 4.4f, 4.1f, 3.3f, 4.9f };

Console.WriteLine("Select a color of Fish by entering the corresponding number \r\n 1. Blue \r\n 2. Yellow \r\n 3. Red \r\n 4. Green");

bool asking = true;
while (asking)
{
    string ColorChoiceNumber = Console.ReadLine();
    int ColorChoiceNumberInt;
    if (int.TryParse(ColorChoiceNumber, out ColorChoiceNumberInt))
    {
        if (ColorChoiceNumberInt >= 1 && ColorChoiceNumberInt <= 4)
        {
            asking = false;
            string[] fish = new string[] { "Blue", "Yellow", "Red", "Green" };
            Console.WriteLine("The Biggest {0} Fish is Fish Number ", fish[ColorChoiceNumberInt - 1]);
        }
        else
        {
            Console.WriteLine("Please only enter a number. It must be 1-4.");
        }
    }
    else
    {
        Console.WriteLine("Please only enter a number. It must be 1-4.");
    }
}

Answer 2

通常，要获得用户的有效输入，您只需要做一些事情：

在致电int

int.TryParse

将变量作为第二个out参数传递给int.TryParse
使用代码检查int.TryParse的返回值以及变量的边界检查作为循环的一部分，因此用户被迫在指定范围内输入有效数字

例如，以下代码首先显示选项，然后在用户输入之前不断询问用户输入有效信息：

// Present the options
Console.WriteLine(" 1. Blue \r\n 2. Yellow \r\n 3. Red \r\n 4. Green");

// This variable will hold their input after the TryParse call 
int ColorChoiceNumberInt;

// Continue to ask for input until they enter an integer between 1 and 4
do
{
    Console.Write("Select a color of Fish by entering the corresponding number (1-4): ");
} while (!int.TryParse(Console.ReadLine(), out ColorChoiceNumberInt) ||
         ColorChoiceNumberInt < 1 ||
         ColorChoiceNumberInt > 4);

我过去所做的就是为此创建一个帮助函数，因此逻辑可以在整个程序中轻松重复使用：

public static int GetIntFromUser(string prompt, int minValue = int.MinValue,
    int maxValue = int.MaxValue)
{
    int input;
    do
    {
        Console.Write(prompt);
    } while (!int.TryParse(Console.ReadLine(), out input) ||
             input < minValue ||
             input > maxValue);

    return input;
}

使用这种辅助方法，您的主要代码突然变得更加简化：

Console.WriteLine(" 1. Blue \r\n 2. Yellow \r\n 3. Red \r\n 4. Green");
int input = GetIntFromUser("Select a fish color (1-4): ", 1, 4);
Console.WriteLine("You entered: " + input);

<强>输出

如果声明不起作用＆amp;用户验证？

2 个答案: