C# Find a matching string by regex

Question

I want to find out, whether my string contains a text like #1, #a, #abc, #123, #abc123dsds and so on... (\'#\' character with one or more characters (digits and letters).

Answer 1

test.Contains("#.+"); does not "understand" regular expressions. It literally checks if the string test literally contains #.+ sequence of characters, which #123 does not contain.

Use Regex.IsMatch instead:

bool matches = Regex.IsMatch(test, "#.+");

Demo.

Answer 2

Or without regex, you can use a combination of StartsWith, Enumerable.Any and char.IsLetterOrDigit methods like;

var s = "#abc123dsds+";
var matches = s.Length > 1 && s.StartsWith("#") && s.Substring(1).All(char.IsLetterOrDigit);

Answer 3

Well this worked for me. \# checks if it starts with #, \w checks if it is a word.

 class Program
{
    static void Main(string[] args)
    {
        string text = "#2";
        string pat = @"\#(\w+)";

        Regex r = new Regex(pat);

        Match m = r.Match(text);

        Console.WriteLine(m.Success);
        Console.ReadKey();
    }
}

Answer 4

String.Contains does not accept a regex.

Use Regex.IsMatch:

var matches = Regex.IsMatch(test, "#.+");

Answer 5

You need to use Regex in order to use a regex pattern.

string text = "#123";
Regex rgx = new Regex("#[a-zA-Z0-9]+");
var match = rgx.Match(text);
bool matche = match.Success)