C#

//using System;//using System.Collections.Generic;//using System.Text;//using System.Collections;

//public class LinkedListNode//{//    public LinkedListNode(Object value)//    {//        this.value = value;//    }

//    //结点数据值//    private object value;//    public object Value//    {//        get//        {//            return this.value;//        }//    }

//    //双向结点指向引用//    private LinkedListNode next;//    private LinkedListNode pre;//    public LinkedListNode Next//    {//        get { return this.next; }//        internal set { this.next = value; }//    }//    public LinkedListNode Pre//    {//        get { return this.pre; }//        internal set { this.pre = value; }//    }//}

结点的数据存储在Object类型的Value字段中。下面我们来创建链表类，该链表类有一个头结点、尾结点和在链表的末尾添加/删除结点的方法：

双向链表类//public class LinkedList//{//    //头结点//    private LinkedListNode head;//    public LinkedListNode Head//    {//        get { return this.head; }//    }//    //尾结点//    private LinkedListNode last;//    public LinkedListNode Last//    {//        get { return this.last; }//    }

//    //在链表尾插入结点//    public LinkedListNode AddNode(Object value)//    {//        LinkedListNode node = new LinkedListNode(value);

//        if (head == null)//        {//            head = node;//            last = head;//        }//        else//        {//            last.Next = node;//            node.Pre = last;//            last = node;//        }

//        return last;//    }

//    //在链表尾删除结点//    public LinkedListNode SubNode()//    {//        if (last == null)//        {//            return null;//        }//        else//        {//            LinkedListNode node = last.Pre;//            node.Next = null;//            last = node;//        }

//        return last;//    }//}

因为是链表，所以我们希望能使用foreach遍历链表，那么，将链表类LinkedList继承IEnumerable接口并实现GetEnumerator()方法：

//using System;//using System.Collections.Generic;using System.;//using System.Text;//using System.Collections;

//namespace ConsoleApplication1//{//    //结点类//    public class LinkedListNode//    {        //        public LinkedListNode(Object value)//        {//            this.value = value;//        }

//        //结点数据值//        private object value;//        public object Value //        {//            get //            {//                return this.value;//            }//        }

//        //双向结点指向引用//        private LinkedListNode next;//        private LinkedListNode pre;//        public LinkedListNode Next //        {//            get { return this.next; }//            internal set { this.next = value;  }//        }//        public LinkedListNode Pre//        {//            get { return this.pre; }//            internal set { this.pre = value; }//        }//    }

//    //双向链表类//    public class LinkedList : IEnumerable//    {//        //头结点//        private LinkedListNode head;//        public LinkedListNode Head //        {//            get { return this.head; }//        }//        //尾结点//        private LinkedListNode last;//        public LinkedListNode Last//        {//            get { return this.last; }//        }

//        //在链表尾插入结点//        public LinkedListNode AddNode(Object value) //        {//            LinkedListNode node = new LinkedListNode(value);

//            if (head == null)//            {//                head = node;//                last = head;//            }//            else//            {//                last.Next = node;//                node.Pre = last;//                last = node;//            }

//            return last;//        }

//        //在链表尾删除结点//        public LinkedListNode SubNode()//        {//            if (last == null)//            {//                return null;//            }//            else//            {//                LinkedListNode node = last.Pre;//                node.Next = null;//                last = node;//            }

//            return last;//        }

//        #region IEnumerable 成员

//        public IEnumerator GetEnumerator()//        {//            LinkedListNode curr = head;//            while (curr != null)//            {//                yield return curr.Value;//                curr = curr.Next;//            }//        }

//        #endregion//    }

//}

//这样我们就可以使用链表了，但该链表中的存储数据只能使Object类型的，这就并不能保证链表中的数据是类型统一的，因此在使用foreach遍历链表时可能出现致命的错误。比如该链表中有整形数据和字符串数据。而且，该链表并不能够为我们提供一个标准的模板。

//下面，我们改进LinkedListNode结点类，使其使用泛型——存储数据的类型使我们任意指定的类型：

using System;using System.Collections.Generic;using System.Text;using System.Collections;

namespace LinkedListNode{            public class LinkedListNode<T>        {            public LinkedListNode(T value)            {                this.value = value;            }

            //结点数据值            private T value;            public T Value            {                get                {                    return this.value;                }            }

            //双向结点指向引用            private LinkedListNode<T> next;            private LinkedListNode<T> pre;            public LinkedListNode<T> Next            {                get { return this.next; }                internal set { this.next = value; }            }            public LinkedListNode<T> Pre            {                get { return this.pre; }                internal set { this.pre = value; }            }        }

        //同样，也需要将链表类改为泛型类：

        public class LinkedList<T> : IEnumerable<T>        {            //头结点            private LinkedListNode<T> head;            public LinkedListNode<T> Head            {                get { return this.head; }            }            //尾结点            private LinkedListNode<T> last;            public LinkedListNode<T> Last            {                get { return this.last; }            }

            //在链表尾插入结点            public LinkedListNode<T> AddNode(T value)            {                LinkedListNode<T> node = new LinkedListNode<T>(value);

                if (head == null)                {                    head = node;                    last = head;                }                else                {                    last.Next = node;                    node.Pre = last;                    last = node;                }

                return last;            }

            //在链表尾删除结点            public LinkedListNode<T> SubNode()            {                if (last == null)                {                    return null;                }                else                {                    LinkedListNode<T> node = last.Pre;                    node.Next = null;                    last = node;                }

                return last;            }

            #region IEnumerable 成员

            public IEnumerator<T> GetEnumerator()            {                LinkedListNode<T> curr = head;                while (curr != null)                {                    yield return curr.Value;                    curr = curr.Next;                }            }

            IEnumerator IEnumerable.GetEnumerator()            {                return GetEnumerator();            }            #endregion        }    class Program    {        static void Main(string[] args)        {            LinkedList<int> list2 = new LinkedList<int>();            list2.AddNode(1);            list2.AddNode(3);            list2.AddNode(5);                       Console.WriteLine("Before Sub:");            foreach (int i in list2)            {                Console.WriteLine(i);            }                        Console.WriteLine("After Sub:");            list2.SubNode();            foreach (int i in list2)            {                               Console.WriteLine(i);            }            Console.ReadLine();        }    }}

//这样我们就保证了链表中数据的统一性，因此可以安全的使用foreach遍历链表了。

//其实，我个人认为，泛型也就是我们在编写代码时并不知道要使用的数据类型是什么，而是在使用代码时规定数据类型的，这样，我们就很容易的创建复用的模板代码，即减少了代码编写的工作，也节省了空间资源。