关于HttpWebRequest下载过程中网络连接断开的问题

[qq5457237]

下载的方法：

            /// <summary>
            /// 下载文件
            /// </summary>
            /// <param name="url">文件路径</param>
            /// <param name="startPos">起始位置</param>
            /// <param name="bytesCount">读取字节数</param>
            /// <returns></returns>
            public byte[] DownLoadFile(string url, int startPos, int bytesCount)
            {
                ServicePointManager.DefaultConnectionLimit = 100;

                System.Net.HttpWebRequest request = (System.Net.HttpWebRequest)System.Net.HttpWebRequest.Create(url);
                request.KeepAlive = false;
                request.AddRange(startPos, startPos + bytesCount - 1); 
                System.Net.WebResponse response =null ;

                try
                {
                    Console.WriteLine("请求数据");
                    response = request.GetResponse();
                }
                catch (WebException wex)
                {
                    Console.WriteLine("请求数据WebException");
                    request.Abort();
                    throw wex;
                }
                catch (Exception ex)
                {
                    Console.WriteLine("请求数据Exception");
                    request.Abort();
                    throw ex;
                }


                try
                {
                    System.IO.Stream receiveStream = response.GetResponseStream();
                    System.IO.BinaryReader readStream = new System.IO.BinaryReader(receiveStream);
                    byte[] buffer = new byte[0];
                    byte[] read = new byte[256];
                    int count = readStream.Read(read, 0, 256);
                    while (count > 0)
                    {
                        Array.Resize<byte>(ref buffer, buffer.Length + count);
                        Array.Copy(read, 0, buffer, buffer.Length - count, count);
                        count = readStream.Read(read, 0, 256);
                    }
                    readStream.Close();
                    return buffer;
                }
                finally
                {
                    response.Close();
                }
            }
        }

调用下载方法的线程：

                    byte[] buffer = null;
                    //当服务器返回的数据长度不等于文件长度时，下载完成
                    while (startPos < FileSize)
                    {
                            string errorInfo = null;
                            try
                            {
                                buffer = HttpDownload.DownLoadFile(url, (int)startPos, blockSize);
                                returnSize = buffer.Length;
                                startPos += returnSize;
                                WriteToFile(buffer);
                                Percent = (int)Math.Floor(startPos * 100.0 / FileSize); 
                            }
                            catch (WebException wex)
                            {
                                errorInfo = "连接失败";
                                Thread.Sleep(3000);
                            }
                            catch (Exception ex)
                            {
                                errorInfo = "连接失败";
                                Thread.Sleep(3000);
                            }
                    }

我设断点调试时测试断网，运行很正常。我不设断点，下载过程中断开网络连接，结果就没反应了，这是和解啊？相当苦闷。。。

[csdn_aspnet]

C# 代码
String url = "http://img04.taobaocdn.com/sns_album/i4/T1yAdWXgdGXXb1upjX.jpg";
String fileName = url.Substring(url.LastIndexOf("/") + 1);
String refer = url.Substring(0, url.LastIndexOf("/") + 1);
System.Net.HttpWebRequest req = System.Net.HttpWebRequest.Create(url) as System.Net.HttpWebRequest;
req.AllowAutoRedirect = true;
req.Referer = refer;
req.UserAgent = "Mozilla/5.0 (Windows; U; Windows NT 6.1; zh-CN; rv:1.9.2.13) Gecko/20101203 Firefox/3.6.13";
System.Net.HttpWebResponse res = req.GetResponse() as System.Net.HttpWebResponse;
System.IO.Stream stream = res.GetResponseStream();
byte[] buffer = new byte[32 * 1024];
int bytesProcessed = 0;
System.IO.FileStream fs = System.IO.File.Create(Server.MapPath(fileName));
int bytesRead;
do
{
bytesRead = stream.Read(buffer, 0, buffer.Length);
fs.Write(buffer, 0, bytesRead);
bytesProcessed += bytesRead;
}
while (bytesRead > 0);
fs.Flush();
fs.Close();
res.Close();

[qq5457237]

这什么乱七八糟的，我想问的是网络断开后，下载怎么没反应了，异常也捕获不到。