using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

public class Program

{

        public static void AddUserConnection(string uid, int userConnection) {

            if (users_dictionary.ContainsKey(uid)) {

                //if the user has already few connected devices and one more device is connecting now so adding to existing list

                ArrayList current_list = users_dictionary[uid];

                current_list.Add(userConnection);

                users_dictionary[uid] = current_list;

                Console.WriteLine("Updated user uid "+uid+" connection list");

            } else {

                // If the new connection is first connection of the user

                users_dictionary.Add(uid, new ArrayList());

                ArrayList current_list = users_dictionary[uid];

                current_list.Add(userConnection);

                users_dictionary[uid] = current_list;

                Console.WriteLine("New user uid " + uid + " connection list created"); 

            }

        }

    public static Dictionary<string, ArrayList> users_dictionary= new Dictionary<string, ArrayList>();

    public static void Main()

    {

        Console.WriteLine("Hello World");

        AddUserConnection("5",65);

        AddUserConnection("6",66);

        AddUserConnection("5",64);

        ArrayList xxx = users_dictionary["5"];

        Console.WriteLine("Latest Updated values of 5th uid Arraylist after updating");         

        for(int i = 0; i<xxx.Count ; i++){

            Console.WriteLine("Value at i = "+i +" is : " + xxx[i].ToString());         

        }

    }

​

}