获取一个网页数据返回的编码类型是gzip，解压后，网页中包含的中文字段变成了乱码，只需要把编码更改为BIG5 ,繁体字就正常显示了！

using ICSharpCode.SharpZipLib.GZip;

//需要添加ICSharpCode.SharpZipLib.dll引用）
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

            //   准备请求  
            string url = "http://www.www.com";

            HttpWebRequest request = (HttpWebRequest)
                    WebRequest.Create(url);
            request.ProtocolVersion = new Version(1, 1);
            request.Accept = "*/*";
            request.Headers.Add("Accept-Encoding:   gzip");
            request.KeepAlive = true;
            request.UserAgent = "Mozilla/4.0   (compatible;   MSIE   6.0;   Windows   NT   5.1;   SV1;   .NET   CLR   1.1.4322;   .NET   CLR   2.0.50727)";
          

            //   读取回应  

            HttpWebResponse response = (HttpWebResponse)request.GetResponse();

            //Console.WriteLine("{0}", response.StatusDescription);
            //foreach (string key in response.Headers.AllKeys)
            //{
            //    Console.WriteLine("{0}:   {1}", key, response.Headers[key]);
            //}

            //   将回应全部读入一个   MemoryStream：  
            MemoryStream ms = new MemoryStream();
            try
            {
                Stream res = response.GetResponseStream();
                byte[] buffer = new byte[8192];
                while (true)
                {
                    int read = res.Read(buffer, 0, 8192);
                    if (read == 0)
                    {
                        //   如果服务器用的是   gzip   的话，只能靠读不出更多数据来判断是否已经读完  
                        Console.WriteLine("Response   is   terminated   due   to   zero   byte   reception.");
                        break;
                    }
                    else
                    {
                        ms.Write(buffer, 0, read);
                    }
                }
            }
            catch (Exception esd)
            {
                //   抛出异常也可能表示已经读完  
                Console.WriteLine("Response   is   terminated   due   to   exception   " + esd.Message);
            }
            finally
            {
                response.Close();
            }
            Console.WriteLine("Response   has   {0}   bytes.", ms.Length);

            //   ms   倒回开头：  

            ms.Seek(0, SeekOrigin.Begin);

            //   用   GZipInputStream   包裹：  

            GZipInputStream gzip = new GZipInputStream(ms);

            //   用   GZipInputStream   读取   ms   的内容并写入   ms2：  

            MemoryStream ms2 = new MemoryStream();
            try
            {
                byte[] buffer = new byte[1];   //   一点一点读——因为这个服务器的gzip没有Footer，读到结尾的时候会出错，所以为了把最后一个字节都读出来，只能一点一点读  

                while (true)
                {
                    int read = gzip.Read(buffer, 0, 1);
                    if (read == 0) break;
                    ms2.Write(buffer, 0, read);

                   
                }
            }
            catch (Exception sa)
            {
                Console.WriteLine("Exception!   " + sa.ToString());
            }
            Console.WriteLine("Unzipped.");

            //   将   ms2（解压后的内容）保存到文件  
            //, System.Text.Encoding.GetEncoding("gb2312")
            Stream  fs;
          
            fs = File.Create("r00000000000.txt");
          
                         
            ms2.Seek(0, SeekOrigin.Begin);
            ms2.WriteTo(fs);  
            fs.Close();
           
            //Encoding code = System.Text.Encoding.GetEncoding("gb2312");
            this.textBox1.Text = System.Text.Encoding.GetEncoding("BIG5").GetString(ms2.ToArray());