我希望用户从键盘按键，然后希望计算机判断键是字母，符号还是数字。 [英] I want the user to press a key from keyboard and then want the computer to tell if the key is a alphabet, symbol or a number.

问题描述

我希望用户从键盘按键，并希望计算机判断键是字母，符号还是数字。但是代码中存在一些错误。你能指出吗？

I want the user to press a key from keyboard and want the computer to tell if the key is a alphabet, symbol or a number. But some error is there in the code. Can you point out ?

Console.WriteLine("type a character");
            int character = int.Parse(Console.ReadLine());
            string type = " ";

            if ((character>=48) && (character<=57))
            {
                type = "integer";
            }

            else if ((character >= 65) && (character <= 90))
            {
                type = "uppercase alphabet";

            }


            else if ((character >= 97) && (character <= 122))
            {
                type = "lowecase character";

            }

            else
            {
                type = "symbol";
            }
           
           
            
            Console.WriteLine("the type of character that you have entered is " +type);
            Console.ReadLine();

推荐答案

问题是当用户键入一个键时，你试图解析它到int：

The problem is that when the user types a key, you try to parse it to an int:

int character = int.Parse(Console.ReadLine());

这意味着从数字1234的字符串表示转换为可以数学处理的整数版本。



因此，如果用户输入8，int.Parse将返回值8 - 小于48，因此它将使所有测试失败。



而是直接使用该字符：

Which means convert from a string representation of a number "1234" to an integer version that can be handle mathematically.

So if the user types an "8" for example, int.Parse will return the value 8 - which is less than 48, so it will fail all your tests.

Instead, use the character directly:

string userInput = Console.ReadLine();
foreach (char c in userInput)
    {
    string type = "unknown";
    if (c >= '0' && c <= '9')
        {
        type = "integer";
        }
    else if ...

或者更好，使用内置函数：

Or better, use the built in functions:

string userInput = Console.ReadLine();
foreach (char c in userInput)
    {
    string type = "symbol";
    if (char.IsDigit(c))
        {
        type = "integer";
        }
    else if (char.IsLetter(c))
        {
        if (char.IsLower(c))
            {
            type = "lowercase character";
            }
        else
            {
            type = "uppercase character";
            }
        }
    ...
    }

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