c# 阻塞隊列

　　/// <summary>    /// 阻塞隊列[.net 4.0 貌似內建了阻塞隊列]    /// </summary>    public class BlockQueue<T>    {        public readonly int SizeLimit = 0;        private Queue<T> _inner_queue = null;        public int Count        {            get { return _inner_queue.Count; }        }        private ManualResetEvent _enqueue_wait = null;        private ManualResetEvent _dequeue_wait = null;        public BlockQueue(int sizeLimit)        {            this.SizeLimit = sizeLimit;            this._inner_queue = new Queue<T>(this.SizeLimit);            this._enqueue_wait = new ManualResetEvent(false);            this._dequeue_wait = new ManualResetEvent(false);        }        public void EnQueue(T item)        {            if (this._IsShutdown == true) throw new InvalidCastException("Queue was shutdown. Enqueue was not allowed.");            while (true)            {                lock (this._inner_queue)                {                    if (this._inner_queue.Count < this.SizeLimit)                    {                        this._inner_queue.Enqueue(item);                        this._enqueue_wait.Reset();                        this._dequeue_wait.Set();                        break;                    }                }                this._enqueue_wait.WaitOne();            }        }        public T DeQueue()        {            while (true)            {                if (this._IsShutdown == true)                {                    lock (this._inner_queue) return this._inner_queue.Dequeue();                }                lock (this._inner_queue)                {                    if (this._inner_queue.Count > 0)                    {                        T item = this._inner_queue.Dequeue();                        this._dequeue_wait.Reset();                        this._enqueue_wait.Set();                        return item;                    }                }                this._dequeue_wait.WaitOne();            }        }        private bool _IsShutdown = false;        public void Shutdown()        {            this._IsShutdown = true;            this._dequeue_wait.Set();        }    }