链表，Enumerator

1.

public class LinkedListNode
    {
        public LinkedListNode(object value)
        {
            this.Value = value;
        }

        public object Value { get; private set; }

        public LinkedListNode Next { get; internal set; }

        public LinkedListNode Prev { get; internal set; }

    }

2.

public class LinkedList : IEnumerable
    {
        public LinkedListNode First { get; private set; }
        public LinkedListNode Last { get; private set; }

        public LinkedListNode AddLast(object node)
        {
            var newNode = new LinkedListNode(node);
            if (null == First)
            {
                First = newNode;
                newNode.Prev = Last;
                Last = First;
            }
            else
            {
                LinkedListNode previous = Last;
                Last.Next = newNode;
                Last = newNode;
                Last.Prev = previous;
            }
            return newNode;
        }

        public IEnumerator GetEnumerator()
        {
            LinkedListNode current = First;
            while (null != current)
            {
                yield return current.Value;
                current = current.Next;
            }
        }

    }

3.使用时：

            LinkedList lstLinked = new LinkedList();
            lstLinked.AddLast(1);
            lstLinked.AddLast(2);
            lstLinked.AddLast(3);
            foreach (int i in lstLinked)
            {
                Response.Write(i + "<br/>");
            }