public sealed class HttpRequestHelper    {        private static string USER_AGENT = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/37.0.2062.124 Safari/537.36";        private static string ACCEPT = "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8";        private static string CONTENT_TYPE = "application/x-www-form-urlencoded; encoding=UTF-8";
        /// <summary>        /// 单例        /// </summary>        private static volatile HttpRequestHelper instance;        private static object syncRoot = new object();        private HttpRequestHelper() { }        public static HttpRequestHelper Instance        {            get            {                if (instance == null)                {                    lock (syncRoot)                    {                        if (instance == null)                        {                            instance = new HttpRequestHelper();                        }                    }                }                return instance;            }        }        /// <summary>        /// Get请求        /// </summary>        /// <param name="queryString">url参数</param>        /// <returns>json格式结果</returns>        public string Get(string URL)        {            string ret = string.Empty;            URL = URL.Replace("ACCESS_TOKEN", WxTokenHelper.Instance.Token);            var request = CreateRequest("GET", URL);            var response = request.GetResponse();            Stream responseStream = response.GetResponseStream();            StreamReader readStream = new StreamReader(responseStream, Encoding.UTF8);            ret = readStream.ReadToEnd();            readStream.Close();            return ret;        }        public string GetToken(string URL)        {            string ret = string.Empty;            var request = CreateRequest("GET", URL);            var response = request.GetResponse();            Stream responseStream = response.GetResponseStream();            StreamReader readStream = new StreamReader(responseStream, Encoding.UTF8);            ret = readStream.ReadToEnd();            readStream.Close();            return ret;        }        /// <summary>        /// Post请求        /// </summary>        /// <param name="URL">请求的URL</param>        /// <param name="jsonData">json格式参数</param>        /// <returns>json格式结果</returns>        public string Post(string URL, string jsonData)        {            string ret = string.Empty;            URL = URL.Replace("ACCESS_TOKEN", WxTokenHelper.Instance.Token);            var request = CreateRequest("POST", URL);            if (!string.IsNullOrWhiteSpace(jsonData))            {                byte[] data =http://www.mamicode.com/ Encoding.UTF8.GetBytes(jsonData);                request.ContentLength = data.Length;                using (var requestStream = request.GetRequestStream())                {                    requestStream.Write(data, 0, data.Length);                };                var response = request.GetResponse() as HttpWebResponse;                using (var responseStream = response.GetResponseStream())                {                    using (var readStream = new StreamReader(responseStream, Encoding.UTF8))                    {                        ret = readStream.ReadToEnd();                    }                }            }            return ret;        }        private HttpWebRequest CreateRequest(string method, string URL)        {            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(URL);            request.Accept = ACCEPT;            request.UserAgent = USER_AGENT;            request.Method = method;            request.ContentType = CONTENT_TYPE;            return request;        }    }