获取微信的access_tokey，处理json格式的数据

#region 获取微信凭证

      public string GetAccessToken(string wechat_id)

      {

          string accessToken = "";

          DataTable dtwecaht = wechatdal.GetList("wechat_id=‘" + wechat_id + "‘").Tables[0];

          if (dtwecaht.Rows.Count > 0)

          {

              string respText = "";

              string wechat_appid = dtwecaht.Rows[0]["wechat_appid"].ToString();

              string wechat_appsecret = dtwecaht.Rows[0]["wechat_appsecret"].ToString();

              string url = string.Format(getAccessTokenUrl, wechat_appid, wechat_appsecret);

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

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

              using (Stream resStream = response.GetResponseStream())

              {

                  StreamReader reader = new StreamReader(resStream, Encoding.Default);

                  respText = reader.ReadToEnd();

                  resStream.Close();

              }

              JavaScriptSerializer Jss = new JavaScriptSerializer();

              Dictionary<string, object> respDic = (Dictionary<string, object>)Jss.DeserializeObject(respText);

              accessToken = respDic["access_token"].ToString();

          }

          return accessToken;

      }

      #endregion 获取微信凭证