如何检查字符串是否包含某些字符串

我想检查C＃中的String s是否包含“ a”或“ b”或“ c”。我正在寻找比使用更好的解决方案

if (s.contains("a")||s.contains("b")||s.contains("c"))

如果您要查找单个字符，则可以使用String.IndexOfAny()。

如果您想要任意字符串，那么我不知道.NET方法可以“直接”实现该功能，尽管可以使用正则表达式。

好吧，总有这样：

public static bool ContainsAny(this string haystack, params string[] needles)
{
    foreach (string needle in needles)
    {
        if (haystack.Contains(needle))
            return true;
    }

    return false;
}

用法：

bool anyLuck = s.ContainsAny("a", "b", "c");

但是，没有什么可以||比照您的比较链的性能了。

这是一个LINQ解决方案，它实际上是相同的，但可扩展性更高：

new[] { "a", "b", "c" }.Any(c => s.Contains(c))

var values = new [] {"abc", "def", "ghj"};
var str = "abcedasdkljre";
values.Any(str.Contains);

您可以尝试使用正则表达式

string s;
Regex r = new Regex ("a|b|c");
bool containsAny = r.IsMatch (s);

如果您需要包含特定值的ContainsAny StringComparison（例如，忽略大小写），则可以使用此String Extensions方法。

public static class StringExtensions
{
    public static bool ContainsAny(this string input, IEnumerable<string> containsKeywords, StringComparison comparisonType)
    {
        return containsKeywords.Any(keyword => input.IndexOf(keyword, comparisonType) >= 0);
    }
}

配合使用StringComparison.CurrentCultureIgnoreCase：

var input = "My STRING contains Many Substrings";
var substrings = new[] {"string", "many substrings", "not containing this string" };
input.ContainsAny(substrings, StringComparison.CurrentCultureIgnoreCase);
// The statement above returns true.

”xyz”.ContainsAny(substrings, StringComparison.CurrentCultureIgnoreCase);
// This statement returns false.

这是“更精细的解决方案”，非常简单

if(new string[] { "A", "B", ... }.Any(s=>myString.Contains(s)))

由于字符串是字符的集合，因此可以在它们上使用LINQ扩展方法：

if (s.Any(c => c == 'a' || c == 'b' || c == 'c')) ...

这将扫描字符串一次并在第一次出现时停止，而不是为每个字符扫描一次字符串直到找到匹配项。

这也可以用于您喜欢的任何表达式，例如检查一系列字符：

if (s.Any(c => c >= 'a' && c <= 'c')) ...

public static bool ContainsAny(this string haystack, IEnumerable<string> needles)
{
    return needles.Any(haystack.Contains);
}

List<string> includedWords = new List<string>() { "a", "b", "c" };
bool string_contains_words = includedWords.Exists(o => s.Contains(o));

// Nice method's name, @Dan Tao

public static bool ContainsAny(this string value, params string[] params)
{
    return params.Any(p => value.Compare(p) > 0);
    // or
    return params.Any(p => value.Contains(p));
}

Any对于任何，All为每

    static void Main(string[] args)
    {
        string illegalCharacters = "!@#$%^&*()\\/{}|<>,.~`?"; //We'll call these the bad guys
        string goodUserName = "John Wesson";                   //This is a good guy. We know it. We can see it!
                                                               //But what if we want the program to make sure?
        string badUserName = "*_Wesson*_John!?";                //We can see this has one of the bad guys. Underscores not restricted.

        Console.WriteLine("goodUserName " + goodUserName +
            (!HasWantedCharacters(goodUserName, illegalCharacters) ?
            " contains no illegal characters and is valid" :      //This line is the expected result
            " contains one or more illegal characters and is invalid"));
        string captured = "";
        Console.WriteLine("badUserName " + badUserName +
            (!HasWantedCharacters(badUserName, illegalCharacters, out captured) ?
            " contains no illegal characters and is valid" :
            //We can expect this line to print and show us the bad ones
            " is invalid and contains the following illegal characters: " + captured));  

    }

    //Takes a string to check for the presence of one or more of the wanted characters within a string
    //As soon as one of the wanted characters is encountered, return true
    //This is useful if a character is required, but NOT if a specific frequency is needed
    //ie. you wouldn't use this to validate an email address
    //but could use it to make sure a username is only alphanumeric
    static bool HasWantedCharacters(string source, string wantedCharacters)
    {
        foreach(char s in source) //One by one, loop through the characters in source
        {
            foreach(char c in wantedCharacters) //One by one, loop through the wanted characters
            {
                if (c == s)  //Is the current illegalChar here in the string?
                    return true;
            }
        }
        return false;
    }

    //Overloaded version of HasWantedCharacters
    //Checks to see if any one of the wantedCharacters is contained within the source string
    //string source ~ String to test
    //string wantedCharacters ~ string of characters to check for
    static bool HasWantedCharacters(string source, string wantedCharacters, out string capturedCharacters)
    {
        capturedCharacters = ""; //Haven't found any wanted characters yet

        foreach(char s in source)
        {
            foreach(char c in wantedCharacters) //Is the current illegalChar here in the string?
            {
                if(c == s)
                {
                    if(!capturedCharacters.Contains(c.ToString()))
                        capturedCharacters += c.ToString();  //Send these characters to whoever's asking
                }
            }
        }

        if (capturedCharacters.Length > 0)  
            return true;
        else
            return false;
    }

您可以使用正则表达式

if(System.Text.RegularExpressions.IsMatch("a|b|c"))

如果您要查找任意字符串，而不仅仅是字符，则可以使用IndexOfAny的重载，该重载从新项目NLib中获取字符串参数：

if (s.IndexOfAny("aaa", "bbb", "ccc", StringComparison.Ordinal) >= 0)