Webclient請求超時設置

Webclient在下載請求時沒法設置請求超時時間和請求讀寫超時時間。WebClient在異步下載時遇到網絡不通等問題時沒有響應超時形成app掛起。

1.Webclient請求超時設置
      重寫Webclient的GetWebRequest方法，爲HttpWebRequest添加請求超時及讀寫超時

      

         protected   override  WebRequest GetWebRequest(Uri address)
         {
            HttpWebRequest request = (HttpWebRequest)base.GetWebRequest(address);
            request.Timeout = 1000 * Timeout;
            request.ReadWriteTimeout = 1000 * Timeout;
            return request;
        }

 

2.WebClient在異步下載

       建立計時器監視響應狀況，過時則取消下載

      

     public   class  Calculagraph
     {
        /// <summary>
        /// 時間到事件
        /// </summary>
        public event TimeoutCaller TimeOver;

        /// <summary>
        /// 開始時間
        /// </summary>
        private DateTime _startTime;
        private TimeSpan _timeout = new TimeSpan(0, 0, 10);
        private bool _hasStarted = false;
        object _userdata;

        /// <summary>
        /// 計時器構造方法
        /// </summary>
        /// <param name="userdata">計時結束時回調的用戶數據</param>
        public Calculagraph(object userdata)
        {
            TimeOver += new TimeoutCaller(OnTimeOver);
            _userdata = userdata;
        }

        /// <summary>
        /// 超時退出
        /// </summary>
        /// <param name="userdata"></param>
        public virtual void OnTimeOver(object userdata)
        {
            Stop();
        }

        /// <summary>
        /// 過時時間(秒)
        /// </summary>
        public int Timeout
        {
            get
            {
                return _timeout.Seconds;
            }
            set
            {
                if (value <= 0)
                    return;
                _timeout = new TimeSpan(0, 0, value);
            }
        }

        /// <summary>
        /// 是否已經開始計時
        /// </summary>
        public bool HasStarted
        {
            get
            {
                return _hasStarted;
            }
        }

        /// <summary>
        /// 開始計時
        /// </summary>
        public void Start()
        {
            Reset();
            _hasStarted = true;
            Thread th = new Thread(WaitCall);
            th.IsBackground = true;
            th.Start();
        }

        /// <summary>
        /// 重置
        /// </summary>
        public void Reset()
        {
            _startTime = DateTime.Now;
        }

        /// <summary>
        /// 中止計時
        /// </summary>
        public void Stop()
        {
            _hasStarted = false;
        }

        /// <summary>
        /// 檢查是否過時
        /// </summary>
        /// <returns></returns>
        private bool checkTimeout()
        {
            return (DateTime.Now - _startTime).Seconds >= Timeout;
        }

        private void WaitCall()
        {
            try
            {
                //循環檢測是否過時
                while (_hasStarted && !checkTimeout())
                {
                    Thread.Sleep(1000);
                }
                if (TimeOver != null)
                    TimeOver(_userdata);
            }
            catch (Exception)
            {
                Stop();
            }
        }
    }

     /// <summary>
    /// 過時時回調委託
    /// </summary>
    /// <param name="userdata"></param>
     public   delegate   void  TimeoutCaller( object  userdata);

 

      

     public   class  CNNWebClient : WebClient
     {

        private Calculagraph _timer;
        private int _timeOut = 10;

        /// <summary>
        /// 過時時間
        /// </summary>
        public int Timeout
        {
            get
            {
                return _timeOut;
            }
            set
            {
                if (value <= 0)
                    _timeOut = 10;
                _timeOut = value;
            }
        }

        /// <summary>
        /// 重寫GetWebRequest,添加WebRequest對象超時時間
        /// </summary>
        /// <param name="address"></param>
        /// <returns></returns>
        protected override WebRequest GetWebRequest(Uri address)
        {
            HttpWebRequest request = (HttpWebRequest)base.GetWebRequest(address);
            request.Timeout = 1000 * Timeout;
            request.ReadWriteTimeout = 1000 * Timeout;
            return request;
        }

        /// <summary>
        /// 帶過時計時的下載
        /// </summary>
        public void DownloadFileAsyncWithTimeout(Uri address, string fileName, object userToken)
        {
            if (_timer == null)
            {
                _timer = new Calculagraph(this);
                _timer.Timeout = Timeout;
                _timer.TimeOver += new TimeoutCaller(_timer_TimeOver);
                this.DownloadProgressChanged += new DownloadProgressChangedEventHandler(CNNWebClient_DownloadProgressChanged);
            }

            DownloadFileAsync(address, fileName, userToken);
            _timer.Start();
        }

        /// <summary>
        /// WebClient下載過程事件，接收到數據時引起
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void CNNWebClient_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)
        {
            _timer.Reset();//重置計時器
        }

        /// <summary>
        /// 計時器過時
        /// </summary>
        /// <param name="userdata"></param>
        void _timer_TimeOver(object userdata)
        {
            this.CancelAsync();//取消下載
        }
    }