How to check if a String contains any of some strings

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

    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;
    }

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