string pattern = @"\b\d{3}-\d{2}-\d{4}\b"; // matches a Social Security Number in the format XXX-XX-XXXX string input = "My SSN is 123-45-6789"; Match match = Regex.Match(input, pattern); if (match.Success) { Console.WriteLine("SSN found: " + match.Value); } else { Console.WriteLine("SSN not found."); }