How to check if a String contains any of some strings

I want to check if a String s, contains "a" or "b" or "c", in C#. I am looking for a nicer solution than using

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

Well, there's always this:

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

    return false;
}

Usage:

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

Nothing's going to match the performance of your chain of || comparisons, however.

Here's a LINQ solution which is virtually the same but more scalable:

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

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

If you are looking for single characters, you can use String.IndexOfAny().

If you want arbitrary strings, then I'm not aware of a .NET method to achieve that "directly", although a regular expression would work.

You can try with regular expression

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

If you need ContainsAny with a specific StringComparison (for example to ignore case) then you can use this String Extentions method.

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);
    }
}

Usage with 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.

This is a "nicer solution" and quite simple

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

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

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

As a string is a collection of characters, you can use LINQ extension methods on them:

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

This will scan the string once and stop at the first occurance, instead of scanning the string once for each character until a match is found.

This can also be used for any expression you like, for example checking for a range of characters:

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

// 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 for any, All for every

    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;
    }

You could have a class for your extension methods and add this one:

    public static bool Contains<T>(this string s, List<T> list)
    {
        foreach (char c in s)
        {
            foreach (T value in list)
            {
                if (c == Convert.ToChar(value))
                    return true;
            }
        }
        return false;
    }

You can use Regular Expressions

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

If this is for a password checker with requirements, try this:

public static bool PasswordChecker(string input)
{
    // determins if a password is save enough
    if (input.Length < 8)
        return false;

    if (!new string[] { "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R",
                        "S", "T", "U", "V", "W", "X", "Y", "Z", "Ä", "Ü", "Ö"}.Any(s => input.Contains(s)))
    return false;

    if (!new string[] { "1", "2", "3", "4", "5", "6", "7", "8", "9", "0"}.Any(s => input.Contains(s)))
    return false;

    if (!new string[] { "!", "'", "§", "$", "%", "&", "/", "(", ")", "=", "?", "*", "#", "+", "-", "_", ".",
                        ",", ";", ":", "`", "´", "^", "°",   }.Any(s => input.Contains(s)))
    return false;

    return true; 
}

This will set a password to have a min length of 8, have it use at least one uppercase char, at least one number, and at least one of the special chars