csharp isalphanumeric

                
                                string str = "ABC123";
 
        if (Regex.IsMatch(str, "^[a-zA-Z0-9]*%%%~COMPRESS~PRE~0~%%%quot;))
        {
            Console.WriteLine("Alphanumeric String");
        }
        else
        {
            Console.WriteLine("Non-Alphanumeric String");
        }