static void Main(string[] args)
        {
            string url = "";
            HttpWebResponse response = CreateGetHttpResponse(url);
            //獲取流
            Stream streamResponse = response.GetResponseStream();
            //使用UTF8解碼
            StreamReader streanReader = new StreamReader(streamResponse,Encoding.UTF8);

            string retString = streanReader.ReadToEnd();
            //先列印內容
            Console.WriteLine(retString);
            //儲存檔案
            SaveFile(retString);


        }
        //建立GET的HTTP請求
        public static HttpWebResponse CreateGetHttpResponse(string url)
        {
            HttpWebRequest request =(HttpWebRequest) WebRequest.Create(url);
            request.ContentType = "text/html;chartset=UTF-8";
            request.UserAgent = "Mozilla / 5.0(Windows NT 10.0; Win64; x64; rv: 48.0) Gecko / 20100101 Firefox / 48.0"; //火狐使用者代理
            request.Method = "GET";
            return (HttpWebResponse)request.GetResponse();
        }
        //儲存檔案
        public static void SaveFile(string  content)
        {
            string dirPath = @"D:\test";

            string filePath = dirPath + @"\getRequest.html"; 
            //先建立儲存的路徑
            if (!Directory.Exists(dirPath))
            Directory.CreateDirectory(dirPath);
            if (!Directory.Exists(filePath))
            using (File.Create(filePath)) ;

            //建立檔案流
            FileStream fs = new FileStream(filePath,FileMode.Create,FileAccess.Write);
            //建立寫入器
            StreamWriter sr = new StreamWriter(fs);
            sr.Write(content);
            sr.Close();
            fs.Close();
        }