using System;

public class ListNode

{

    //Is this comment visible?

    public ListNode(string id) : this(id, null){}

​

    public ListNode(string id, ListNode tail)

    {

        Id = id;

        Next = tail;

    }

    public string Id{get;}

    public ListNode Next{get;}

    public void Iter( Action<ListNode> op)

    {

        op(this);

        if (null != Next) 

        {

            Next.Iter(op);

        }

    }

}

​

public class Program

{

    public static void Main()

    {

        var list = new ListNode( "n0", new ListNode ("n1", new ListNode ("n2", new ListNode ("n3", new ListNode ("END")))));

        list.Iter( n => Console.WriteLine(n.Id));

    }

}