using System;

using System.Collections.Generic;

using System.Collections.ObjectModel;

public class Program

{

    public static void Main()

    {

          var l = new List<int>{1,2,3,4,5};

  var c = new Collection<int>(l);

​

  l.Add(6);

​

  Console.WriteLine(String.Join(",", c));

​

    }

}