"WX": {
    "AppId": "wx88822730803edd44",
    "AppSecret": "75b269042e8b5026e6ed14aa24ba9353",
    "Templates": {
      "Audit": {
        "TemplateId": "aBaIjTsPBluYtj2tzotzpowsDDBGLhXQkwrScupnQsM",
        "PageUrl": "/pages/index/formAudit?formId={0}&tableId={1}",
        "MiniprogramState": "developer",
        "Lang": "zh_TW",
        "Data": {
          "Title": "thing6",
          "Content": "thing19",
          "Date": "date9"
        }
      }
    },
    "SignatureToken": "aaaaaa",
    "MessageSendUrl": "https://api.weixin.qq.com/cgi-bin/message/subscribe/send?access_token={0}",
    "AccessTokenUrl": "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid={0}&secret={1}"
  }

二、编写通用类加载配置

using System;
using System.Text;
using System.Security.Cryptography;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Configuration.Json;

namespace WXERP.Services
{
    /// <summary>
    /// 项目公有静态类
    /// </summary>
    public class Common
    {
        /// <summary>
        /// 獲取根目錄
        /// </summary>
        public static string AppRoot => Environment.CurrentDirectory;// AppContext.BaseDirectory;
        /// <summary>
        /// 獲取項目配置
        /// </summary>
        public static IConfiguration Configuration { get; set; }
        /// <summary>
        /// 加載項目配置
        /// </summary>
        static Common()
                {
            Configuration = new ConfigurationBuilder()
            .Add(new JsonConfigurationSource
            {
                Path = "appsettings.json",
                ReloadOnChange = true //当appsettings.json被修改时重新加载      
            })
            .Build();
        }

        /// <summary>
        /// SHA1加密
        /// </summary>
        /// <param name="content">需要加密的字符串</param>
        /// <returns>返回40位大寫字符串</returns>
        public static string SHA1(string content)
                {
            try
            {
                SHA1 sha1 = new SHA1CryptoServiceProvider();
                byte[] bytes_in = Encoding.UTF8.GetBytes(content);
                byte[] bytes_out = sha1.ComputeHash(bytes_in);
                sha1.Dispose();
                string result = BitConverter.ToString(bytes_out);
                result = result.Replace("-", "");
                return result;
            }
            catch (Exception ex)
            {
                throw new Exception("Error in SHA1: " + ex.Message);
            }
        }

    }
}

三、编写HttpHelper请求类

using System;
using System.Text;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Threading.Tasks;
using System.Collections.Generic;

namespace WXERP.Services
{
    /// <summary>
    /// HTTP請求輔助類
    /// </summary>
    public class HttpHelper
    {
        /// <summary>
        /// post同步請求
        /// </summary>
        /// <param name="url">地址</param>
        /// <param name="postData">數據</param>
        /// <param name="contentType">application/xml、application/json、application/text、application/x-www-form-urlencoded</param>
        /// <param name="headers">請求頭</param>        
        /// <returns></returns>
        public static string HttpPost(string url, string postData = null, string contentType = null, Dictionary<string, string> headers = null)
                {
            using HttpClient client = new HttpClient();

            if (headers != null)
            {
                foreach (var header in headers)
                    client.DefaultRequestHeaders.Add(header.Key, header.Value);
            }

            postData ??= "";
            using HttpContent httpContent = new StringContent(postData, Encoding.UTF8);
            if (contentType != null)
                httpContent.Headers.ContentType = new MediaTypeHeaderValue(contentType);

            HttpResponseMessage response = client.PostAsync(url, httpContent).Result;
            return response.Content.ReadAsStringAsync().Result;
        }

        /// <summary>
        /// post異步請求
        /// </summary>
        /// <param name="url">地址</param>
        /// <param name="postData">數據</param>
        /// <param name="contentType">application/xml、application/json、application/text、application/x-www-form-urlencoded</param>
        /// <param name="timeOut">請求超時時間</param> 
        /// <param name="headers">請求頭</param>        
        /// <returns></returns>
        public static async Task<string> HttpPostAsync(string url, string postData = null, string contentType = null, int timeOut = 30, Dictionary<string, string> headers = null)
                {
            using HttpClient client = new HttpClient();
            client.Timeout = new TimeSpan(0, 0, timeOut);

            if (headers != null)
            {
                foreach (var header in headers)
                    client.DefaultRequestHeaders.Add(header.Key, header.Value);
            }

            postData ??= "";
            using HttpContent httpContent = new StringContent(postData, Encoding.UTF8);
            if (contentType != null)
                httpContent.Headers.ContentType = new MediaTypeHeaderValue(contentType);

            HttpResponseMessage response = await client.PostAsync(url, httpContent);
            return await response.Content.ReadAsStringAsync();
        }

        /// <summary>
        /// get同步請求
        /// </summary>
        /// <param name="url">地址</param>
        /// <param name="headers">請求頭</param>
        /// <returns></returns>
        public static string HttpGet(string url, Dictionary<string, string> headers = null)
                {
            using HttpClient client = new HttpClient();

            if (headers != null)
            {
                foreach (var header in headers)
                    client.DefaultRequestHeaders.Add(header.Key, header.Value);
            }

            HttpResponseMessage response = client.GetAsync(url).Result;
            return response.Content.ReadAsStringAsync().Result;
        }

        /// <summary>
        /// get異步請求
        /// </summary>
        /// <param name="url"></param>
        /// <param name="headers"></param>
        /// <returns></returns>
        public static async Task<string> HttpGetAsync(string url, Dictionary<string, string> headers = null)
                {
            using HttpClient client = new HttpClient();

            if (headers != null)
            {
                foreach (var header in headers)
                    client.DefaultRequestHeaders.Add(header.Key, header.Value);
            }

            HttpResponseMessage response = await client.GetAsync(url);
            return await response.Content.ReadAsStringAsync();
        }

    }

}

四、在sqlserver下存储并获取openid，这个主要是因为提交消息并不是在微信小程序端，如果是在微信小程序上发起订阅消息，可以忽略这个步骤

// 创建数据库表

create table TBSF_Conmmunicate_WXUser
(
  ID int identity(1,1) primary key,
  Staff_ID varchar(10),
  OpenId varchar(50),
  SessionKey varchar(50),
  UnionId varchar(50),
  IsValid bit,
)

// SqlHelper数据库辅助类来自于CommunicationOperateDBUtility，可以自己编写

using System.Data;
using System.Text;
using CommunicationOperateDBUtility;

namespace WXERP.Services.CommunicationOperateDAL
{
    /// <summary>
    /// 微信信息
    /// </summary>
    public class WXInforDeal
    {
        private SqlHelper sqlHelper = null;
        /// <summary>
        /// 初始化數據庫輔助對象
        /// </summary>
        /// <param name="con"></param>
        public WXInforDeal(object con)
                {
            sqlHelper = new SqlHelper(con);
        }
        /// <summary>
        /// 獲取微信登陸用戶信息
        /// </summary>
        /// <param name="staffIdList">工號</param>
        /// <returns></returns>
        public DataSet GetLoginUserInfo(string staffIdList)
                {
            DataSet ds = new DataSet();
            StringBuilder stringBuilder = new StringBuilder();
            stringBuilder.Append(" SELECT distinct OpenId FROM ");
            stringBuilder.Append(" TBSF_Conmmunicate_WXUser WHERE Staff_ID IN (");
            stringBuilder.Append(staffIdList);
            stringBuilder.Append(")");
            string strSql = stringBuilder.ToString();
            sqlHelper.DBRunSql(strSql, ref ds);
            return ds;
        }
    }
}

五、编写订阅消息基类模型

using System;
using System.Data;
using Newtonsoft.Json;
using System.Collections.Generic;
using WXERP.Services.CommunicationOperateDAL;

namespace WXERP.Models
{
    /// <summary>
    /// 訂閲消息請求模型
    /// </summary>
    public class SubscribeMessageModel
    {
        /// <summary>
        /// 初始化審核訂閲消息
        /// </summary>
        /// <param name="dbTransOrCnn">數據庫事務</param>
        /// <param name="nextAuditStaffId">下一個審核通知用戶工號</param>
        public SubscribeMessageModel(object dbTransOrCnn, string nextAuditStaffId)
                {
            WXInforDeal wxInfoDeal = new WXInforDeal(dbTransOrCnn);
            DataSet wxUserInfo = wxInfoDeal.GetLoginUserInfo(nextAuditStaffId);
            if (wxUserInfo != null && wxUserInfo.Tables.Count > 0 && wxUserInfo.Tables[0].Rows.Count > 0)
            {
                Touser = wxUserInfo.Tables[0].Rows[0]["OpenId"].ToString();
            }
        }
        /// <summary>
        /// 消息接收者的openid
        /// </summary>
        [JsonProperty("touser")]
        public string Touser { get; set; }
        /// <summary>
        /// 消息模板ID
        /// </summary>
        [JsonProperty("template_id")]
        public string TemplateId { get; set; }
        /// <summary>
        /// 點擊模板卡片后的跳轉頁面，僅限本小程序内的頁面，支持帶參數（示例index?foo=bar），該字段不填則不跳轉
        /// </summary>
        [JsonProperty("page")]
        public string Page { get; set; }
        /// <summary>
        /// 跳轉小程序類型：developer開發版、trial體驗版、formal正式版，默认为正式版
        /// </summary>
        [JsonProperty("miniprogram_state")]
        public string MiniprogramState { get; set; }
        /// <summary>
        /// 進入小程序查看的語言類型，支持zh_CN(簡體中文)、en_US(英文)、zh_HK(繁體中文)、zh_TW(繁體中文)，默認為zh_CN
        /// </summary>
        [JsonProperty("lang")]
        public string Lang { get; set; }
        /// <summary>
        /// 模板内容
        /// </summary>
        [JsonProperty("data")]
        public Dictionary<string, DataValue> Data { get; set; }
    }
    /// <summary>
    /// 模板内容關鍵字
    /// </summary>
    public class DataValue
    {
        /// <summary>
        /// 訂閲消息參數值
        /// </summary>
        [JsonProperty("value")]
        public string Value { get; set; }
    }

    /// <summary>
    /// 小程序訂閲消息響應模型
    /// </summary>
    public class SubscribeMsgResponseModel
    {
        /// <summary>
        /// 錯誤代碼
        /// </summary>
        public int Errcode { get; set; }
        /// <summary>
        /// 錯誤信息
        /// </summary>
        public string Errmsg { get; set; }
    }

    /// <summary>
    /// 小程序獲取token響應模型
    /// </summary>
    public class AccessTokenResponseModel
    {
        /// <summary>
        /// 小程序訪問token
        /// </summary>
        public string Access_token { get; set; }
        /// <summary>
        /// Token過期時間，單位秒
        /// </summary>
        public int Expires_id { get; set; }
        /// <summary>
        /// Token創建時間
        /// </summary>
        public DateTime Create_time { get; set; }
        /// <summary>
        /// 刷新以後的Token
        /// </summary>
        public string Refresh_token { get; set; }
        /// <summary>
        /// 小程序用戶唯一標識，如果用戶未關注公衆號，訪問公衆號網頁也會產生
        /// </summary>
        public string Openid { get; set; }
        /// <summary>
        /// 用戶授權的作用域，使用逗號分隔
        /// </summary>
        public string Scope { get; set; }
    }

}

六、实现消息订阅基类，下面的SetTemplateData方法根据自己的情况设置需要推送消息的内容，如果以后有其他订阅消息模板，新增一个类实现SubscribeMessageModel

using System;
using System.Collections.Generic;
using Newtonsoft.Json;
using BestSoft.Common.Resources;
using BSFWorkFlow.Common.GeneralUtility;
using WXERP.Models;

namespace WXERP.Services.SubscribeMessage
{
    /// <summary>
    /// 審核訂閲消息
    /// </summary>
    public class AuditSubscribeMessage : SubscribeMessageModel
    {
        private string page;
        private string lang;
        private Dictionary<string, DataValue> data;
        /// <summary>
        /// 設置小程序OpenId
        /// </summary>
        /// <param name="dbTransOrCnn">數據庫事務</param>
        /// <param name="nextAuditStaffId">下一個審核通知用戶工號</param>
        public AuditSubscribeMessage(object dbTransOrCnn, string nextAuditStaffId)
            : base(dbTransOrCnn, nextAuditStaffId)
                {

        }
        /// <summary>
        /// 消息模板ID
        /// </summary>
        [JsonProperty("template_id")]
        public new string TemplateId => Common.Configuration["WX:Templates:Audit:TemplateId"];

        /// <summary>
        /// 設置小程序訂閲消息跳轉頁面
        /// </summary>
        /// <param name="formId"></param>
        /// <param name="tableId"></param>
        public void SetPageUrl(string formId, string tableId)
                {
            Page = string.Format(Common.Configuration["WX:Templates:Audit:PageUrl"],
                formId, tableId);
        }
        /// <summary>
        /// 點擊模板卡片后的跳轉頁面
        /// </summary>
        [JsonProperty("page")]
        public new string Page
        {
            get
            {
                return page;
            }
            set
            {
                page = value;
                return;
            }
        }
        /// <summary>
        /// 跳轉小程序類型
        /// </summary>
        [JsonProperty("miniprogram_state")]
        public new string MiniprogramState => Common.Configuration["WX:Templates:Audit:MiniprogramState"];
        /// <summary>
        /// 進入小程序查看的語言類型，支持zh_CN(簡體中文)、en_US(英文)、zh_HK(繁體中文)、zh_TW(繁體中文)，默認為zh_CN
        /// </summary>
        [JsonProperty("lang")]
        public new string Lang
        {
            get
            {
                lang = Common.Configuration["WX:Templates:Audit:Lang"];
                if (!string.IsNullOrEmpty(MyHttpContext.Current.Request.Headers["bsLanKind"]))
                    lang = MyHttpContext.Current.Request.Headers["bsLanKind"];

                return lang;
            }
            set
            {
                lang = value;
                return;
            }
        }
        /// <summary>
        /// 設置審核訂閲消息數據
        /// </summary>
        /// <param name="operation">審核動作：通過、否決、作廢、退回</param>
        /// <param name="itemAuditStatus">審核狀態：1代表審核完畢</param>
        /// <param name="currentWorkflowName">審核標題</param>
        public void SetTemplateData(WFAuditOperation operation, WFAuditItemStatus itemAuditStatus, string currentWorkflowName)
                {
            string tip_msg = "";
            switch (operation)
            {
                case WFAuditOperation.AuditPassAndAgree:
                    if (itemAuditStatus == WFAuditItemStatus.SuccessfulToFinishAllAudits)
                        tip_msg = GeneralFunction.ReplaceNullOrEmptyStr(SourcesWarehouse.GetStringSources("WFEngine_FinishAuditTip"), "您的單據已審核完成!");
                    else
                        tip_msg = GeneralFunction.ReplaceNullOrEmptyStr(SourcesWarehouse.GetStringSources("WFEngine_AuditAgreeTip"), "您有一筆新單據待審核!");
                    break;
                case WFAuditOperation.AuditPassButDegree:
                    tip_msg = GeneralFunction.ReplaceNullOrEmptyStr(SourcesWarehouse.GetStringSources("WFEngine_AuditDegreeTip"), "您提交的單據等待異議!");
                    break;
                case WFAuditOperation.AuditAbort:
                    tip_msg = GeneralFunction.ReplaceNullOrEmptyStr(SourcesWarehouse.GetStringSources("WFEngine_AuditAbortTip"), "您提交的單據已被作廢!");
                    break;
                case WFAuditOperation.AuditBack:
                    tip_msg = GeneralFunction.ReplaceNullOrEmptyStr(SourcesWarehouse.GetStringSources("WFEngine_AuditBackTip"), "您提交的單據已被退回修正!");
                    break;
            }

            string title = Common.Configuration["WX:Templates:Audit:Data:Title"];
            string content = Common.Configuration["WX:Templates:Audit:Data:Content"];
            string date = Common.Configuration["WX:Templates:Audit:Data:Date"];
            Dictionary<string, DataValue> data = new Dictionary<string, DataValue>()
            {
                {title, new DataValue{ Value= currentWorkflowName }},
                {content, new DataValue{ Value= tip_msg }},
                {date, new DataValue{ Value= DateTime.Now.ToShortDateString() }}
            };

            Data = data;
        }
        /// <summary>
        /// 審核訂閲消息數據
        /// </summary>
        [JsonProperty("data")]
        public new Dictionary<string, DataValue> Data
        {
            get
            {
                return data;
            }
            set
            {
                data = value;
                return;
            }
        }

    }
}

七、编写发送订阅消息，消息推送配置签名认证

using System;
using System.Threading.Tasks;
using System.Collections.Generic;
using Newtonsoft.Json;
using WXERP.Models;

namespace WXERP.Services
{
    /// <summary>
    /// 系統消息上下文
    /// </summary>
    public class MessageContext
    {
        /// <summary>
        /// 獲取AccessToken的全局鎖
        /// </summary>
        private readonly static object SyncLock = new object();

        private static Dictionary<string, AccessTokenResponseModel> tokenCache = new Dictionary<string, AccessTokenResponseModel>();

        /// <summary>
        /// 發送訂閲消息
        /// </summary>
        /// <param name="msg">消息内容</param>
        /// <param name="errMsg">可能由於獲取的token錯誤</param>
        /// <returns></returns>
        public static bool SendSubscribeMsg(SubscribeMessageModel msg, out string errMsg)
                {
            errMsg = "";
            try
            {
                string token = GetAccessToken();
                if (token.Length < 20)
                {
                    errMsg = "Failed to send subscription message, Access token error!";
                    return false;
                }
                string url = string.Format(Common.Configuration["WX:MessageSendUrl"], token);
                string requestJson = JsonConvert.SerializeObject(msg);
                string responseJson = HttpHelper.HttpPost(url, requestJson, "application/json", null);

                var msgResponse = JsonConvert.DeserializeObject<SubscribeMsgResponseModel>(responseJson);
                if (msgResponse.Errcode != 0)
                {
                    errMsg = string.Format("Failed to send subscription message, {0}", msgResponse.Errmsg);
                    return false;
                }
            }
            catch (Exception exp)
            {
                throw new Exception("SendSubscribeMsg: " + exp.Message);
            }
            return true;
        }

        /// <summary>
        /// 獲取小程序訪問token
        /// </summary>
        /// <returns></returns>
        private static string GetAccessToken()
                {
            lock (SyncLock)
            {
                string appid = Common.Configuration["WX:AppId"];
                string appsecret = Common.Configuration["WX:AppSecret"];
                string accessTokenUrl = string.Format(Common.Configuration["WX:AccessTokenUrl"], appid, appsecret);

                AccessTokenResponseModel result = null;
                if (tokenCache.ContainsKey(appid))
                    result = tokenCache[appid];

                if (result == null)
                {
                    string responseJson = HttpHelper.HttpGet(accessTokenUrl, null);
                    result = JsonConvert.DeserializeObject<AccessTokenResponseModel>(responseJson);
                    result.Create_time = DateTime.Now;
                    tokenCache.Add(appid, result);
                }
                else if (DateTime.Compare(result.Create_time.AddSeconds(result.Expires_id), DateTime.Now) < 1)
                                 {
                    string responseJson = HttpHelper.HttpGet(accessTokenUrl, null);
                    result = JsonConvert.DeserializeObject<AccessTokenResponseModel>(responseJson);
                    result.Create_time = DateTime.Now;
                    tokenCache[appid] = result;
                }
                return result.Access_token;
            }
        }

        /// <summary>
        /// 驗證消息來自於微信服務器
        /// </summary>
        /// <param name="signature">微信加密簽名，signature結合了開發者填寫的token、timestamp、nonce</param>
        /// <param name="timestamp">時間戳</param>
        /// <param name="nonce">隨機數</param>
        /// <returns></returns>
        public async Task<bool> CheckSignature(string signature, string timestamp, string nonce)
                {
            string token = Common.Configuration["WX:SignatureToken"];
            string[] tmpArr = { token, timestamp, nonce };
            Array.Sort(tmpArr);
            string tmpStr = string.Join("", tmpArr);
            tmpStr = Common.SHA1(tmpStr);

            if (!tmpStr.Equals(signature, StringComparison.OrdinalIgnoreCase))
                return false;

            await Task.CompletedTask;
            return true;
        }

    }
}

八、编写消息推送配置签名认证控制器

using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using WXERP.Services;

namespace WXERP.Controllers
{
    /// <summary>
    /// 消息控制器
    /// </summary>
    [Route("api/[controller]")]
    [ApiController]
    public class MessageController : ControllerBase
    {
        private readonly MessageContext _context;
        /// <summary>
        /// 初始化消息
        /// </summary>
        public MessageController()
                {
            _context = new MessageContext();
        }

        /// <summary>微信消息</summary>
        /// <remarks>驗證消息來自於微信服務器</remarks>
        /// <param name="signature">微信加密簽名，signature結合了開發者填寫的token、timestamp、nonce</param>
        /// <param name="timestamp">時間戳</param>
        /// <param name="nonce">隨機數</param>
        /// <param name="echostr">隨機字符串</param>
        /// <returns></returns>
        [HttpGet("checkSignature")]
        [AllowAnonymous]
        public async void CheckSignature(string signature,string timestamp,string nonce,string echostr)
                {
            bool result = await _context.CheckSignature(signature, timestamp, nonce);
            if (result)
            {
                HttpContext.Response.ContentType = "text/plain; charset=utf-8";
                await HttpContext.Response.WriteAsync(echostr);
            }
            else
            {
                HttpContext.Response.StatusCode = 409;
                HttpContext.Response.ContentType = "text/plain; charset=utf-8";
                await HttpContext.Response.WriteAsync("error");
            }
        }

    }
}

九、调用小程序订阅消息，需要自己实现其他逻辑

//@iFormSaveDAL.GetTran  数据库链接事务，如果发送消息失败，应该回滚提交的表单数据
//@wFControl.NextAuditNotifyStaffIDStr  下一个审核用户的工号
//@auditPageData.FormID  表单编号
//@auditPageData.MainRecordID 表单数据ID
//@operationByCode  一个枚举类型，前端传递的：审核通过、作废、退回等
//@wFControl.ItemAuditStatus  一个枚举类型，如果全部审核完毕为1，否则为0
//@wFControl.CurrentWorkflowName  当前流程的名称，例如：请假单审核
//@SaveAfterInfo  全局字符变量，用于保存结果信息

AuditSubscribeMessage auditMsg = new AuditSubscribeMessage(iFormSaveDAL.GetTran, wFControl.NextAuditNotifyStaffIDStr);
auditMsg.SetPageUrl(auditPageData.FormID, auditPageData.MainRecordID);
auditMsg.SetTemplateData(operationByCode, wFControl.ItemAuditStatus, wFControl.CurrentWorkflowName);
if (!string.IsNullOrEmpty(auditMsg.Touser))
{
    if (!MessageContext.SendSubscribeMsg(auditMsg, out messageStr))
    {
        SaveAfterInfo = messageStr;
        return false;
    }
}

有不懂或需要改正的欢迎留言！

.netcore 3.1 C# 微信小程序发送订阅消息