C#微信开发之旅(六)：生成带参数的二维码

主要用来推广并统计数据，当用户扫描带参数二维码时，微信会推送消息到我们的服务器，此时可以根据参数了解到用户是从哪个渠道关注的。话不多少，先来代码：

#region 生成二维码

        /// <summary>
        /// 获取Ticket
        /// </summary>
        /// <returns></returns>
        private static string CreateTicket(string scene_id)
        {
            var token = AccessToken.Instance;

            if (string.IsNullOrEmpty(token.Access_Token))
                throw new ArgumentNullException("Access_Token");

            string url = string.Format(WeiXinConst.WeiXin_Ticket_CreateUrl, token.Access_Token);
            string postData = WeiXinConst.WeiXin_QrCodeTicket_Create_JsonString.Replace("{0}", scene_id);

            string result = HttpClientHelper.PostResponse(url, postData);
            Ticket ticket = JsonConvert.DeserializeObject<Ticket>(result); //HttpClientHelper.PostResponse<Ticket>(url, postData);

            if (ticket == null || string.IsNullOrEmpty(ticket.ticket))
            {
                ErrorMessage msg = JsonConvert.DeserializeObject<ErrorMessage>(result);
                if (msg.TokenExpired)
                    return CreateTicketByNewAccessToken(scene_id);
            }
            return ticket.ticket;
        }

        /// <summary>
        /// 当AccessToken过期时 调用此方法
        /// </summary>
        /// <param name="scene_id"></param>
        /// <returns></returns>
        private static string CreateTicketByNewAccessToken(string scene_id)
        {
            var token = AccessToken.NewInstance;

            if (string.IsNullOrEmpty(token.Access_Token))
                throw new ArgumentNullException("Access_Token");

            string url = string.Format(WeiXinConst.WeiXin_Ticket_CreateUrl, token.Access_Token);
            string postData = WeiXinConst.WeiXin_QrCodeTicket_Create_JsonString.Replace("{0}", scene_id);

            Ticket ticket = HttpClientHelper.PostResponse<Ticket>(url, postData);

            if (ticket == null || string.IsNullOrEmpty(ticket.ticket))
                throw new Exception("Ticket为Null，AccessToken:" + token.Access_Token);
            return ticket.ticket;
        }


        /// <summary>
        /// 根据Ticket获取二维码图片保存在本地
        /// </summary>
        /// <param name="scene_id">二维码场景id</param>
        /// <param name="imgPath">图片存储路径</param>
        public static void SaveQrCodeImage(string scene_id, string imgPath)
        {
            string Ticket = CreateTicket(scene_id);

            if (Ticket == null)
                throw new ArgumentNullException("Ticket");

            //ticket需 urlEncode
            string stUrl = string.Format(WeiXinConst.WeiXin_QrCode_GetUrl, HttpUtility.UrlEncode(Ticket));

            HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(stUrl);

            req.Method = "GET";

            using (WebResponse wr = req.GetResponse())
            {
                HttpWebResponse myResponse = (HttpWebResponse)req.GetResponse();
                string strpath = myResponse.ResponseUri.ToString();

                WebClient mywebclient = new WebClient();

                try
                {
                    mywebclient.DownloadFile(strpath, imgPath);
                }
                catch (Exception)
                {
                    throw new Exception("获取二维码图片失败！");
                }
            }
        }

        /// <summary>
        /// 根据SceneId 获取 二维码图片流
        /// </summary>
        /// <param name="scene_id"></param>
        /// <returns></returns>
        public static Stream GetQrCodeImageStream(string scene_id)
        {
            string Ticket = CreateTicket(scene_id);

            if (Ticket == null)
                throw new ArgumentNullException("Ticket");

            //ticket需 urlEncode
            string strUrl = string.Format(WeiXinConst.WeiXin_QrCode_GetUrl, HttpUtility.UrlEncode(Ticket));
            try
            {
                System.Net.Http.HttpClient client = new System.Net.Http.HttpClient();
                Byte[] bytes = client.GetByteArrayAsync(strUrl).Result;
                return new MemoryStream(bytes);
            }
            catch
            {
                throw new Exception("获取二维码图片失败！");
            }
        }

        #endregion

生成带参数的二维码，需要先获取Ticket（内置 token过期处理），再根据Ticket获取二维码（两个方法：保存到本地 以及 返回Stream）。

下面是调用代码：

            string scene_id = "1";//场景Id，扫描生产的二维码 会带这个id，可以做推广、统计用

            //获取二维码流
            System.IO.Stream stream = WeiXinHelper.GetQrCodeImageStream(scene_id);

            //二维码图片存储路径
            string path = Server.MapPath("~/Document/QrCode/" + scene_id + ".jpg"); 
            //直接保存二维码到本地
            WeiXinHelper.SaveQrCodeImage("1", path);