public string Convert(string str, ConvertRule cr)
 {
     foreach (ConvertRule convertRule in cr.GetInvocationList())
     {
         str = convertRule(str);
     }
     return(str);
 }
        static void Main(string[] args)
        {
            ConvertRule rd = RemoveDigits;
            ConvertRule rs = RemoveSpaces;

            Converter cv = new Converter();

            string test1 = "1njon423n5jn36";
            string test2 = "  jj k l [ effw  wfwerf";
            string test3 = "23 45 4f 6hj 9k";

            Console.WriteLine(cv.Convert(test1, rd));
            Console.WriteLine(cv.Convert(test2, rs));

            ConvertRule rds = rd + rs;

            foreach (ConvertRule a in rds.GetInvocationList())
            {
                Console.WriteLine(a?.Invoke(test3));
            }
        }