实现下载问题!!!!!!

#region 远程采集图片
        /// <summary>
        /// 远程采集图片
        /// </summary>
        /// <param name="imageUrl">图片路径(http形式)</param>
        /// <param name="filepath">保存路径</param>
        /// <returns>是否成功</returns>
        public static bool DownLoadImage(string imageUrl, string filepath)
        {
            Uri _uri = new Uri(imageUrl);            if (_uri != null)
            {
                int _index = imageUrl.LastIndexOf("/") + 1;                string _fileName = imageUrl.Substring(_index, imageUrl.Length - _index);                HttpWebRequest _request = (HttpWebRequest)WebRequest.Create(_uri);
                try
                {
                    _request.KeepAlive = false;
                    _request.ProtocolVersion = HttpVersion.Version10;
                    _request.Proxy = System.Net.WebProxy.GetDefaultProxy();//allow auto redirects from redirect headers
                    _request.AllowAutoRedirect = true;//maximum of 10 auto redirects
                    _request.MaximumAutomaticRedirections = 10;//30 second timeout for _request
                    _request.Timeout = (int)new TimeSpan(0, 0, 60).TotalMilliseconds;//give the crawler a name. //_request.UserAgent = "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)";//User-agent HTTP 标头的值。默认值为空引用                    HttpWebResponse _response = (HttpWebResponse)_request.GetResponse();
                    Stream _stream = _response.GetResponseStream();
                    Bitmap _bitmap = new Bitmap(_stream);                    _bitmap.Save(filepath + "\\" + _fileName);
                }
                catch
                {
                    return false;
                }
            }
            else
            {
                return false;
            }            return true;
        }
        #endregion