public class GenericList
    {
        private class Node
        {
            //当前节点值
            private T data;
            public T Data
            {
                get { return data; }
                set { data = value; }
            }
            //节点的下一个节点
            private Node next;
            public Node Next
            {
                get { return next; }
                set { next = value; }
            }
            //节点的上一个节点
            private Node last;
            public Node Last
            {
                get { return last; }
                set { last = value; }
            }
            public Node(T t)
            {
                data = t;
                next = null;
            }
        }
        private Node firstNode;
        private Node lastNode;
        public void AddNode(T t)
        {
            Node node = new Node(t);
            node.Last = lastNode;
            if (lastNode != null)
                lastNode.Next = node;
            lastNode = node;
            if (firstNode == null)
            {
                firstNode = node;
            }
        }
        //要在自定义泛型集合上迭代
        //必须实现该接口
        public IEnumerator GetEnumerator()
        {
            Node current = firstNode;
            while (current != null)
            {
                //yield return表达式以枚举对象返回
                yield return current.Data;
                current = current.Next;
            }
        }
    }

class GenericListTestTwo
    {
        static void Main()
        {
            // 类型参数为int
            GenericList list = new GenericList();
            for (int a = 0; a < 5; a++)
            {
                list.AddNode(a);
            }
            foreach (int i in list)
            {
                System.Console.WriteLine(i);
            }
            //类型参数为string
            GenericList strList = new GenericList();
            strList.AddNode("First Node");
            strList.AddNode("Second Node");
            foreach(string s in strList)
            {
                System.Console.WriteLine(s);
            }
            Console.Read();
        }
    }