using System;

​

class LinkItem<T>

{

    public LinkItem<T> Prev{get;set;}

    public LinkItem<T> Next{get;set;}

    public T Item {get;set;}

}

​

class MyLinkList<T> 

{

    LinkItem<T> _last;

    public void Add(T valItem)

    {

        var newItem  = new LinkItem<T>(){Item = valItem};

        if (_last != null)

        {

            _last.Next = newItem;

            newItem.Prev = _last;

        }   

        _last = newItem;

    }

}

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

    }

}