向网站发送请求并将答复写入txt

            string url="abc";

            HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(url);

            request.Method = "GET";

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

            Stream s = response.GetResponseStream();

            string strDate = "";

            string strValue = "";

            StreamReader reader = new StreamReader(s, Encoding.UTF8);

            while ((strDate = reader.ReadLine()) != null)

            {

                strValue += strDate + "\r\n";

            }

            FileStream fs = new FileStream("D:\\text.txt", FileMode.Append);

            StreamWriter sw = new StreamWriter(fs, Encoding.Default);

            sw.Write(strValue);

            sw.Close();

            fs.Close();

存在以下问题：

1 当网站答复为json格式时，答复中的中文均为乱码