c# - 如何检查字符串中每个字符的数据类型？

Question

我是 C# 新手，所以可能会遇到一些错误。非常感谢任何帮助/指导。

我想将可接受的字符串输入限制为:

• a-z
• A-Z
• 连字符
• 时期

如果字符是字母、连字符或句号，则接受。任何其他内容都会返回错误。

我目前的代码是

string foo = "Hello!";
foreach (char c in foo)
{
    /*  Is there a similar way
        To do this in C# as 
        I am basing the following
        Off of my Python 3 knowledge
    */

    if (c.IsLetter == true) // *Q: Can I cut out the == true part ?*
    {
        // Do what I want with letters
    }
    else if (c.IsDigit == true)
    {
        // Do what I want with numbers
    }
    else if (c.Isletter == "-") // Hyphen | If there's an 'or', include period as well
    {
        // Do what I want with symbols
    }
}

我知道这是一组非常糟糕的代码。

写这篇文章的时候我有一个想法:是否可以创建一个允许的字符列表并根据该列表检查变量？

类似于:

foreach (char c in foo)
{
    if (c != list)
    {
        // Unaccepted message here
    }
    else if (c == list)
    {
        // Accepted
    }
}

提前致谢!

Answer 1

使用 Regex 即可轻松完成:

using System.Text.RegularExpressions;

var isOk = Regex.IsMatch(foo, @"^[A-Za-z0-9\-\.]+$");

纲要:

match from the start
|              set of possible matches
|              |
|+-------------+
||             |any number of matches is ok
||             ||match until the end of the string
||             |||
vv             vvv
^[A-Za-z0-9\-\.]+$ 
  ^  ^  ^  ^ ^
  |  |  |  | |
  |  |  |  | match dot
  |  |  |  match hyphen
  |  |  match 0 to 9
  |  match a-z (lowercase)
  match A-Z (uppercase)