内部异常捕获问题


        public static void Download()
        {
            int count = 0;
            try
            {
                HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://img.bimg.126.net/photo/c7bckFJxdJxSwQLIy76HTQ==/1755840904721658663.jpg");
                using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
                {                    byte[] buffer = new byte[64];                    string temppath = "g:\\1755840904721658663.jpg";
                    using (System.IO.Stream downloadStream = response.GetResponseStream())
                    {                        using (FileStream saveFileStream = new FileStream(temppath, FileMode.Create, FileAccess.Write, FileShare.None))
                        {
                            int readSize = 0;                            while (true)
                            {
                                readSize = downloadStream.Read(buffer, 0, buffer.Length);
                                if (readSize <= 0) break;
                                saveFileStream.Write(buffer, 0, readSize);                            }
                            Console.WriteLine("弹出");                        }
                    }
                }
            }
            catch (System.Net.Sockets.SocketException ex)
            {
                Console.WriteLine("网络中断");
            }
            catch (Exception ex)
            {
                //throw ex;
                Console.WriteLine("异常类型：{0}", ex.GetType());
                Console.WriteLine("异常信息：{0}", ex.Message);
                Console.WriteLine("异常来源：{0}", ex.Source);
                Console.WriteLine("异常堆栈：{0}", ex.StackTrace);
                Console.WriteLine("内部异常：{0}", ex.InnerException);            }        }
上面是一段简单的下载代码，网络很不稳定，下载大文件时老断，就去捕获它的错误信息，如下
异常类型：System.IO.IOException
异常信息：无法从传输连接中读取数据: 远程主机强迫关闭了一个现有的连接。。
内部异常：System.Net.Sockets.SocketException (0x80004005): 远程主机强迫关闭了一
个现有的连接。
   在 System.Net.Sockets.Socket.Receive(Byte[] buffer, Int32 offset, Int32 size,
 SocketFlags socketFlags)
   在 System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 s
ize)虽然IOException的能捕获错误信息，但是它不是关于网络连接的错误信息吧？
但内部异常的，System.Net.Sockets.SocketException ，是关于网络的吧？但是这个异常捕获不到，
那位前辈能说说，谢谢