using System;

using System.Collections;

​

public class Program

{

    public static void Main()

    {

        // instantiate new list structure

        var list1 = new LinkedListString();

        // add items to the list

        list1.AddLast("2");

        list1.AddLast("4");

        list1.AddLast("6");

        //iterate though the items in the list and print results to the console     

        foreach (string i in list1)

        {

            Console.WriteLine(i);

        }

    }

}

​

public class LinkedListNode

{

    public LinkedListNode(string value)

    {

        this.Value = value;

    }

​

    public string Value

    {

        get;

        private set;

    }

​

    public LinkedListNode Next

    {

        get;

        internal set;

    }

​

    public LinkedListNode Prev

    {

        get;

        internal set;

    }

}

​

public class LinkedListString : IEnumerable

{

    public LinkedListNode First

    {

        get;

        private set;

    }

​

    public LinkedListNode Last

    {

        get;

        private set;

    }

​

    public LinkedListNode AddLast(string node)

    {

        var newNode = new LinkedListNode(node);

        if (First == null)

        {

            First = newNode;

            Last = First;

        }

        else

        {

            LinkedListNode previous = Last;

            Last.Next = newNode;

            Last = newNode;

            Last.Prev = previous;

        }

​

        return newNode;

    }

​

    public IEnumerator GetEnumerator()

    {

        LinkedListNode current = First;

        while (current != null)

        {

            yield return current.Value;

            current = current.Next;

        }

    }

}