Example: use C ＃ NET teaches you to do WeChat official account development (7) -- location message for general message processing.

Today, let's talk about a very important news ：GPS Location message .

One 、 Application, for example,

There are too many location-based applications , such as ：

Look for people nearby ;

Find nearby merchants ;

Calculate the distance from the designated person or merchant ;

Use Baidu map 、 Tencent map 、 Ali map api Interface , Mark on the map , Realize visual map ;

Calculate the distribution fee, etc .

Two 、 How to obtain wechat user location information

WeChat official account can get WeChat users in two ways. GPS Location ,

First, common message mode , User in wechat app Active location information is sent to the official account. , As shown in the figure below ：

Second, wechat app Automatically remind wechat users whether to upload location information , After the user allows , You can send location information to official account regularly. , As shown in the figure below ：

This method requires interface authority to be configured in the official account of WeChat. （ See the picture below ）, Turn on auto accept user information , You can choose to send every few minutes , You can also choose to send it every time you enter the official account. , Specific application needs , When there are a large number of fans , Send more frequently , The greater the server load .

The second method is explained in detail during subsequent event message processing , I won't go into that .

3、 ... and 、 Message format sent by wechat server

Location messages sent by users , After being processed by wechat server , The formation is as follows XML Send format to your server ： 

<xml>
  <ToUserName><![CDATA[toUser]]></ToUserName>
  <FromUserName><![CDATA[fromUser]]></FromUserName>
  <CreateTime>1351776360</CreateTime>
  <MsgType><![CDATA[location]]></MsgType>
  <Location_X>23.134521</Location_X>
  <Location_Y>113.358803</Location_Y>
  <Scale>20</Scale>
  <Label><![CDATA[ Location information ]]></Label>
  <MsgId>1234567890123456</MsgId>
</xml>

  Four 、 Specific implementation of the source code

After receiving the content sent by wechat server , First, the specified interface page AccessWx.aspx Identify the type of information , Then give it to the specified message processing class to process and respond . In the first of this series 1 This article introduces AccessWx.aspx.cs Introducing namespaces at the beginning of using QinMing.Weixin.MessageHandlerLocation;

And perfect the following paragraph , Add the location message processing link given in this article .  

			else if(MsgType == "location")
			{
				LocationMessageDeal tmd = new LocationMessageDeal();
				Response.Write(tmd.DealResult(weixinXML));				
			}

In namespace QinMing.Weixin.MessageHandlerLocation Next create a new class LocationMessageDeal, It is used to process video messages sent by wechat server . Remember to put the class source code file in App_Code Under the table of contents ！ The following is the location message processing source code ：
QinMingWeixinMessageHandlerLocation.cs The contents of the document are as follows ：

using System;
using System.Web;
using System.Xml;
using System.Text;
using System.Data;
using System.Data.SqlClient;
using System.IO;
using System.Net;
using QinMing.Config;
using QinMing.Weixin.ReturnContent;
//using QinMing.WeixinSendTemplateMessage;

namespace QinMing.Weixin.MessageHandlerLocation
{
	// Video message processing 
    public class LocationMessageDeal :System.Web.UI.Page
    {

		public string DealResult(string weixinXML)
        {
            string content = DealLocation(weixinXML);  
            return content;
        }

        public string DealLocation(string weixinXML)
        {
            XmlDocument doc = new XmlDocument();
            doc.LoadXml(weixinXML);
            XmlNodeList list = doc.GetElementsByTagName("xml");
            XmlNode xn = list[0];
            string FromUserName = xn.SelectSingleNode("//FromUserName").InnerText;   // After paying attention to the encryption of users openid
            string ToUserName = xn.SelectSingleNode("//ToUserName").InnerText;       // Public micro signal source ID
            string strresponse = "";
			
			// Users report location information by sending location to the official account. 
			string Latitude = xn.SelectSingleNode("//Location_X").InnerText;
			string Longitude = xn.SelectSingleNode("//Location_Y").InnerText;
			string ScaleW = xn.SelectSingleNode("//Scale").InnerText;
			string AddrLabel = xn.SelectSingleNode("//Label").InnerText;
			UpdateLocation(FromUserName, Latitude, Longitude, ScaleW, AddrLabel);
			
			ReturnMsg rm = new ReturnMsg();
			strresponse = rm.ReturnText(FromUserName, ToUserName, " Your location information has been included , If there is any change later , Please resend the location .");			
			
			// Inform the customer service staff that wechat users have updated their location 
			//QinMingWeixinSendTemplateMessage SendTempMsg = new QinMingWeixinSendTemplateMessage();
			//SendTempMsg.SendTempMsgRemind(" Administrators openid", " Send location message to customer ", "");  

            return strresponse; 
        }
		
		// Update the position longitude and latitude information in the wechat user table 
		public void UpdateLocation(string FromUserName, string Latitude, string Longitude , string ScaleW, string AddrLabel)
		{
            SqlConnection conn = new SqlConnection(QinMingConfig.DatabaseConnStr);
            conn.Open();
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = conn;
			
			cmd.CommandText = "update weixin_user_info set latitude='" + Latitude + "',longitude='" + Longitude + "',"
			    + "precision='" + ScaleW + "',addr_label='" + AddrLabel + "' where open_id='" + FromUserName + "'";
            cmd.ExecuteScalar();
			
            if (conn.State == ConnectionState.Open)
            {
                conn.Close();
                conn.Dispose();
            }
		}

    }
}

User information table used in the previous code weixin_user_info Create the statement as follows ：（ This table will be frequently used later , Here is the table structure ）

CREATE TABLE weixin_user_info
(
	open_id nvarchar(40) NULL,          -- The only encoding of WeChat users in official account 
	nickname nvarchar(60) NULL,         -- nickname 
	sex int NULL,                       -- Gender 
	language nvarchar(20) NULL,         -- Language 
	city nvarchar(40) NULL,             -- City 
	province nvarchar(60) NULL,         -- Province 
	country nvarchar(60) NULL,          -- Township 
	headimgurl nvarchar(400) NULL,      -- Avatar image link 
	unionid nvarchar(60) NULL,          -- official account 、 Applet 、 Unique user ID shared by web page code scanning login 
	remark nvarchar(20) NULL,           -- remarks 
	groupid nvarchar(20) NULL,          -- User group 
	subscribe_scene nvarchar(60) NULL,  -- Source of concern 
	qr_scene nvarchar(10) NULL,         -- Scan type 
	qr_scene_str nvarchar(100) NULL,    -- Code scanning type description 
	remove_flag nvarchar(10) NULL,      -- Cancel attention 
	latitude nvarchar(50) NULL,         --GPS latitude 
	longitude nvarchar(50) NULL,        --GPS longitude 
	precision nvarchar(50) NULL,        --GPS precision 
	addr_label nvarchar(200) NULL,      --GPS Location address description 
	guishu_openid nvarchar(40) NULL,    -- References openid
	guishu_mobile nvarchar(12) NULL,    -- The mobile number of the recommender 
	guishu_type nvarchar(20) NULL,      -- Recommended source type 
	join_time datetime NULL,            -- Focus on time 
	personal_score bigint NULL          -- User points 
)

5、 ... and 、 One example of location information application ： Calculate the meter between two longitudes and latitudes 、 Kilometer value

    // Get two GPS Distance between , The unit is rice. 
	MapHelper mh1 = new MapHelper();
	double d1 = mh1.GetDistanceMeter(Lat1, Lon1, Lat2, Lon2);

	// Get two GPS Distance between , The unit is rice. 
	MapHelper mh2 = new MapHelper();
	double d2 = mh2.GetDistanceKilometre(Lat1, Lon1, Lat2, Lon2);

Used MapHelper Class source code is as follows ：

    public class MapHelper
    {
        private const double earth_radius = 6378.137;// Earth radius 
        private static double rad(double d)
        {
            return d * Math.PI / 180.0;
        }
        /// <summary>
        ///  Calculation 2 The distance between the points 
        /// </summary>
        /// <param name="lat1"> spot A</param>
        /// <param name="lng1"> spot A</param>
        /// <param name="lat2"> spot B</param>
        /// <param name="lng2"> spot B</param>
        /// <returns> km </returns>
        public double GetDistanceKilometre(double lat1, double lng1, double lat2, double lng2)
        {
            double radLat1 = rad(lat1);
            double radLat2 = rad(lat2);
            double a = radLat1 - radLat2;
            double b = rad(lng1) - rad(lng2);
            double s = 2 * Math.Asin(Math.Sqrt(Math.Pow(Math.Sin(a / 2), 2) +
            Math.Cos(radLat1) * Math.Cos(radLat2) * Math.Pow(Math.Sin(b / 2), 2)));
            s = s * earth_radius;
            s = Math.Round(s * 10000) / 10000;
            return s;
        }
 
        /// <summary>
        ///  Calculation 2 The distance between the points 
        /// </summary>
        /// <param name="lat1"> spot A</param>
        /// <param name="lng1"> spot A</param>
        /// <param name="lat2"> spot B</param>
        /// <param name="lng2"> spot B</param>
        /// <returns> rice </returns>
        public double GetDistanceMeter(double lat1, double lng1, double lat2, double lng2)
        {
            double radLat1 = rad(lat1);
            double radLat2 = rad(lat2);
            double a = radLat1 - radLat2;
            double b = rad(lng1) - rad(lng2);
            double s = 2 * Math.Asin(Math.Sqrt(Math.Pow(Math.Sin(a / 2), 2) +
            Math.Cos(radLat1) * Math.Cos(radLat2) * Math.Pow(Math.Sin(b / 2), 2)));
            s = s * earth_radius;
            s = Math.Round(s * 10000) / 10;
            return s;
        }
    }