链表C#实现

    /// <summary>
    /// 结点类
    /// Summary description for ListNode.
    /// </summary>
    public class ListNode
    {
        public ListNode(int NewValue)
        {
            Value = NewValue;
        }
 
        public ListNode Previous;// 前一个
        public ListNode Next;// 后一个
        public int Value;// 值
    }


    /// <summary>
    /// 链表类
    /// -----------------------------------------------------------------
    ///   定义结点之后，开始类线性表的操作编程了.在LIST 类中,采用了，
    /// Head ,Tail,Current,三个指针，使用Append,MoveFrist,MovePrevious，
    /// MoveNext,MoveLast,Delete,InsertAscending,InsertUnAscending
    /// ,Clear实现移动，添加，删除,升序插入,降序插入，
    ///  清空链表操作，GetCurrentValue（） 方法取得当前的值。
    /// </summary>
    public class Clist
    {
        public Clist()
        {
            //构造函数
            //初始化
            ListCountValue = 0;
            Head = null;
            Tail = null;
        }

        private ListNode Head;// 头指针
        private ListNode Tail;// 尾指针
        private ListNode Current;// 当前指针
        private int ListCountValue;// 链表数据的个数

        /// <summary>
        /// 尾部添加数据
        /// </summary>
        public void Append(int DataValue)
        {
            ListNode NewNode = new ListNode(DataValue);

            if (IsNull()) //如果头指针为空
            {
                Head = NewNode;
                Tail = NewNode;
            }
            else
            {
                Tail.Next = NewNode;
                NewNode.Previous = Tail;
                Tail = NewNode;
            }
            Current = NewNode;
            ListCountValue += 1;//链表数据个数加一
        }

        /// <summary>
        /// 删除当前的数据
        /// </summary>
        public void Delete()
        {
            if (!IsNull())//若为空链表
            {
                if (IsBof())//若删除头
                {
                    Head = Current.Next;
                    Current = Head;
                    ListCountValue -= 1;
                    return;
                }
                if (IsEof())//若删除尾
                {
                    Tail = Current.Previous;
                    Current = Tail;
                    ListCountValue -= 1;
                    return;
                }
                //若删除中间数据
                Current.Previous.Next = Current.Next;
                Current = Current.Previous;
                ListCountValue -= 1;

                return;
            }
        }

        /// <summary>
        /// 向后移动一个数据
        /// </summary>
        public void MoveNext()
        {
            if (!IsEof())
            {
                Current = Current.Next;
            }
        }

        /// <summary>
        /// 向前移动一个数据
        /// </summary>
        public void MovePrevious()
        {
            if (!IsBof())
            {
                Current = Current.Previous;
            }
        }

        /// <summary>
        /// 移动到第一个数据
        /// </summary>
        public void MoveFrist()
        {
            Current = Head;
        }

        /// <summary>
        /// 移动到最后一个数据
        /// </summary>
        public void MoveLast()
        {
            Current = Tail;
        }

        /// <summary>
        /// 判断是否为空链表
        /// </summary>
        public bool IsNull()
        {
            if (ListCountValue == 0)
            {
                return true;
            }
            else
            {
                return false;
            }
        }

        /// <summary>
        /// 判断是否为到达尾部
        /// </summary>
        public bool IsEof()
        {
            if (Current == Tail)
            {
                return true;
            }
            else
            {
                return false;
            }
        }

        /// <summary>
        /// 判断是否为到达头部
        /// </summary>
        public bool IsBof()
        {
            if (Current == Head)
            {
                return true;
            }
            else
            {
                return false;
            }
        }

        public int GetCurrentValue()
        {
            return Current.Value;
        }

        /// <summary>
        /// 取得链表的数据个数
        /// </summary>
        public int ListCount
        {
            get
            {
                return ListCountValue;
            }
        }

        /// <summary>
        /// 清空链表
        /// </summary>
        public void Clear()
        {
            MoveFrist();
            while (!IsNull())
            {
                Delete();//若不为空链表,从尾部删除
            }
        }

        /// <summary>
        /// 在当前位置前插入数据
        /// </summary>
        public void Insert(int DataValue)
        {
            ListNode NewNode = new ListNode(DataValue);
            if (IsNull())
            {
                Append(DataValue);//为空表，则添加
                return;
            }

            if (IsBof())
            {
                //为头部插入
                NewNode.Next = Head;
                Head.Previous = NewNode;
                Head = NewNode;
                Current = Head;
                ListCountValue += 1;

                return;
            }

            //中间插入
            NewNode.Next = Current;
            NewNode.Previous = Current.Previous;
            Current.Previous.Next = NewNode;
            Current.Previous = NewNode;
            Current = NewNode;
            ListCountValue += 1;

        }

        /// <summary>
        /// 进行升序插入
        /// 参数：InsertValue 插入的数据
        /// </summary>
        public void InsertAscending(int InsertValue)
        {
            if (IsNull())//为空链表
            {
                Append(InsertValue);//添加
                return;
            }

            MoveFrist();//移动到头

            if ((InsertValue < GetCurrentValue()))
            {
                Insert(InsertValue);//满足条件，则插入，退出
                return;
            }

            while (true)
            {
                if (InsertValue < GetCurrentValue())
                {
                    Insert(InsertValue);//满族条件，则插入，退出
                    break;
                }

                if (IsEof())
                {
                    Append(InsertValue);//尾部添加
                    break;
                }

                MoveNext();//移动到下一个指针

            }
        }

        /// <summary>
        /// 进行降序插入
        /// 参数：InsertValue 插入的数据
        /// </summary>
        public void InsertUnAscending(int InsertValue)
        {
            if (IsNull())//为空链表
            {
                Append(InsertValue);//添加
                return;
            }

            MoveFrist();//移动到头

            if (InsertValue > GetCurrentValue())
            {
                Insert(InsertValue);//满足条件，则插入，退出
                return;
            }

            while (true)
            {
                if (InsertValue > GetCurrentValue())
                {
                    Insert(InsertValue);//满族条件，则插入，退出
                    break;
                }

                if (IsEof())
                {
                    Append(InsertValue);//尾部添加
                    break;
                }

                MoveNext();//移动到下一个指针
            }
        }
    }