using System;

using System.Text.RegularExpressions;

public class Program

{

    // numeric string with length = 8

    public static void Main()

    {

        string[] ids = new string[]{"12345678", "123", "", "-12341234", "asdf", "123412341234"};

        string pattern = "^[0-9]{8}$";

        Regex regex = new Regex(pattern);

        for(int i = 0; i < ids.Length; i++)

        {

            Match match = regex.Match(ids[i]);

            Console.WriteLine(ids[i] + ": " + match.Success);

        }

    }

}