如何检查字符串是否包含给定字符列表之外的字符 [英] How to check if a string contains chars that are outside of a given char list

问题描述

我有一个字符串，我需要检查此字符串是否包含不在给定列表中的任何字符.

I have a string, and I need to check if this string contains any chars that are not in a given list.

假设我允许使用此字符， new char [] {'0'，'1'，'2'，'3'，'4'，'5'，'6'，'7'，'8'，'9'，'.'}

Suppose i have this allowed chars new char[] { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' , '.'}

如果字符串为"54323.5"-没关系！

If string is "54323.5" - this will be ok !

如果字符串是"543g23.5"-这将是不可能的，因为它包含的"g"不在我允许的字符列表中.

If string is "543g23.5" - this won't be ok since it contains "g" which is not in the list of my allowed chars.

一个空字符串被认为是无效的.

An empty string is considered invalid.

我正在尝试通过使用"IndexOfAny()"来实现这一目标，但是到目前为止还没有运气.当然，将所有不允许的字符传递给此方法将不是解决方案.

I am trying to achieve this by using "IndexOfAny()" but with no luck so far. Of course passing all the unallowed chars to this method won't be a solution.

请注意，允许的字符列表可能会更改，并且基于列表更改来更改验证算法不被视为解决方案.

Please note that the list of the allowed chars may change and changing the validation algorithm based on the list change is not considered a solution.

对于那些问我尝试过的代码的人，这里是:

For you guys that asked me the code that I tried, here it is:

        private bool CheckInvalidInput(string stringToCheck)
    {
        char[] allowedChars = new char[] { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };

        var chars = Enumerable.Range(0, char.MaxValue + 1)
                  .Select(i => (char)i)
                  .ToArray();

        var unallowedChars = chars.Except(allowedChars).ToArray();

        bool validString = true;
        if(stringToCheck.IndexOfAny(unallowedChars) != -1)
        {
            validString = false;
        }

        return validString;
    }

希望您会提供更好的解决方案:D.

Hope that you will come with a better solution :D.

推荐答案

这很容易实现. string 类型实现了 IEnumerable< char> ，因此您可以使用LINQ All 方法来检查其所有字符是否都满足谓词.在您的情况下，谓词是每个字符都包含在 allowedChars 集中，因此您可以使用 Contains 方法:

This is straightforward to achieve. The string type implements IEnumerable<char>, so you can use the LINQ All method to check that all its characters satisfy a predicate. In your case, the predicate is that each character is contained in the allowedChars set, so you can use the Contains method:

private static bool CheckInvalidInput(string stringToCheck, IEnumerable<char> allowedChars)
{
    return stringToCheck.All(allowedChars.Contains);
}

如果您的 allowedChars 设置变大，则需要将其转换为 HashSet< char> 以获得更好的性能.

If your allowedChars set gets large, you would want to convert it to a HashSet<char> for better performance.

完整示例:

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

public class Test
{
    public static void Main()
    {
        // var allowedChars = new char[] { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '.' };
        var allowedChars = "0123456789.";

        Console.WriteLine(CheckInvalidInput("54323.5", allowedChars));   // True
        Console.WriteLine(CheckInvalidInput("543g23.5", allowedChars));  // False
    }

    private static bool CheckInvalidInput(string stringToCheck, IEnumerable<char> allowedChars)
    {
        return stringToCheck.All(allowedChars.Contains);
    }
}

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