using System;

using System.Collections.Generic;                   

public class Program

{

    public static void Main()

    {

         var set = new settings();

        Console.WriteLine("users in config before our method");

         foreach (var user in set.conf.users)

            {

                Console.WriteLine("USer ID : {0} " ,user.ID);

            }

        int listIndex = 0;

        int newID = 12;

​

        set.userPropertys(listIndex).ID = newID ;

        Console.WriteLine("users in config after our method");

         foreach (var user in set.conf.users)

            {

                Console.WriteLine("USer ID : {0} " ,user.ID);

            }

        Console.WriteLine("See Id of first user updated");

    }

     public class settings

    {

        public config conf = new config();

        public user userPropertys(int listIndex)

        {

            return conf.users[listIndex];

        }

​

        public class config

        {

            public List<user> users = new List<user>() {

            new user(){ID=1},

            new user(){ID=10}          

            };

        }

    }

​

    public class user

    {

        public int ID;

    }

}