. Net core - a queuing system for wechat official account

Part1 Preface

Wechat code scanning login , Wechat scanning code to obtain queuing information is very common , But you know how the principle is realized ？ Today I'm going to solve your doubts ！

Part2 Overall process

1 The browser requests the server to get the QR code image

The browser generates a unique value uuid

adopt uuid Get the QR code with parameters , take uuid As key Put in redis Cache server

Server generation uuid Back to the browser

adopt uuid Get the QR code with parameters , take uuid As key Put in redis Cache server

2 User scan code

Scan QR code by mobile phone , Then carry it with your mobile phone uuid And user information to send a request to the server of the mobile phone , The mobile server will carry it after receiving it uuid Go to redis The server queries the user .

• Sweep the login code ：

After querying the user successfully, a Token To web server , By parsing this Token You can take out the user's information , Then the browser successfully logged into wechat .

• Push queue information Call the template message after querying the user successfully , Then the queue information push succeeds .

Part3 Development

Take wechat scanning code to obtain queuing information as an example

First step , obtain uuid

To simplify the process , And generated by the front end uuid.

The second step , obtain Access token

public async Task<string> GetAccessToken()
        {
            var accesstoken = await "https://api.weixin.qq.com/cgi-bin/token"
                    .SetQueryParams(new
                    {
                        grant_type = "client_credential",
                        appid = WeixinSetting.Appid,
                        secret = WeixinSetting.Appsecret
                    })
                 .GetJsonAsync<AccessToken>();
            return accesstoken.Access_Token;
        }

The third step , Use uuid Create QR code ticket

public async Task<string> GetTicket(string uuid, string token)
        {


            var accesstoken = await "https://api.weixin.qq.com/cgi-bin/qrcode/create"
                .SetQueryParams(new
                {
                    access_token = token
                })
                .PostJsonAsync(new
                {
                    expire_seconds = 604800,
                    action_name = "QR_STR_SCENE",
                    action_info = new
                    {
                        scene = new
                        {
                            scene_str = uuid
                        }
                    }
                }).ReceiveJson<TicketUrl>();



            return accesstoken.Ticket;


        }

Step four , adopt ticket In exchange for QR code

If you have passed ticket Requirements for generating QR code , It can be handled by itself , If there is no interface that can directly access wechat official account

public async Task<byte[]> GetQrCode(string ticket)
        {
            return await "https://mp.weixin.qq.com/cgi-bin/showqrcode"
             .SetQueryParams(new
             {
                 ticket = ticket
             })
          .GetBytesAsync();

        }

The complete code is as follows

[HttpGet("GetQrCode")]
        public async Task<IActionResult> GetQrCode(string uuid)
        {
            return new FileContentResult( await _qrCodeServices.ShowQrCode(uuid), "image/jpeg");
        }

public async Task<byte[]> ShowQrCode(string uuid)
        {
            string token = await GetAccessToken();
            string ticket = await GetTicket(uuid, token);
            return await GetQrCode(ticket);
        }

In this way, we will generate a QR code image with parameters

Step six , Wechat scanning code for callback

Handle the message template push logic in the callback method

[HttpPost]
        public async Task<string> post()
        {
            IHttpBodyControlFeature httpBodyControlFeature = Request.HttpContext.Features.Get<IHttpBodyControlFeature>();
            if (httpBodyControlFeature != null )
            {
                httpBodyControlFeature.AllowSynchronousIO = true;
            }
            string content = new StreamReader(Request.Body).ReadToEnd();

            await qrCodeServices.PushTemplateMessage(content);
            return "success";

        }

public async Task PushTemplateMessage(string content)
        {
            XmlDocument doc = new XmlDocument();
            doc.LoadXml(content);
            if (doc.DocumentElement["MsgType"].InnerText != "Event") return;
            if (doc.DocumentElement["Event"].InnerText != "SCAN") return;
            string value = doc.DocumentElement["FromUserName"].InnerText;

            string token = await GetAccessToken();
            var accesstoken = await "https://api.weixin.qq.com/cgi-bin/message/template/send"
          .SetQueryParams(new
          {
              access_token = token
          })
          .PostJsonAsync(new
          {
              touser = value,
              template_id = "i4h4yHvgMgIoJ8-Mr49XcpbhMxmRXFJ5EF5DoOTGOMc",
              data = new
              {
                  first = new
                  {
                      value = " Current queue location ",
                      color = "#173177"
                  },
                  keyword1 = new
                  {
                      value = "70",
                      color = "#173177"
                  },
                  keyword2 = new
                  {
                      value = "40 minute ",
                      color = "#173177"
                  }

              }
          });
        }

In this way, it is successful to scan wechat code to obtain queuing information

Part4 summary

The article comes from every bit of life , This is also my improvisation , If you have better skills , Welcome to exchange , It is much joyful to share the joy than enjoy alone. , That's all for this article , I hope it will help you .