public class XQueue<T>

    {

        /// <summary>

        /// 第一个元素

        /// </summary>

        private static XQueueItem<T> _top;

        /// <summary>

        /// 最后一个元素

        /// </summary>

        private static XQueueItem<T> _last;

        /// <summary>

        /// 长度

        /// </summary>

        private int _length;

        /// <summary>

        /// 容量

        /// </summary>

        /// <returns></returns>

        public int Count()

        {

            return _length;

        }

        /// <summary>

        /// 入队

        /// </summary>

        /// <param name="t"></param>

        public void Enqueue(T t)

        {

            var item = new XQueueItem<T> { Item = t };

            if (_top == null)

            {

                _last = _top = item;

            }

            else

            {

                _last.Next = item;

                item.Prev = _last;

            }

            _length++;

        }

        /// <summary>

        /// 出队

        /// </summary>

        /// <returns></returns>

        public T DeQueue()

        {

            if (_length == )

            {

                throw new Exception("队列为空");

            }

            T t = _last.Item;

            _last = _last.Prev;

            return t;

        }

        internal class XQueueItem<T>

        {

            /// <summary>

            /// 当前元素

            /// </summary>

            public T Item;

            /// <summary>

            /// 下一个元素

            /// </summary>

            public XQueueItem<T> Next;

            /// <summary>

            /// 上一个元素

            /// </summary>

            public XQueueItem<T> Prev;

        }

    }