微信公众号开发--.net core接入

　　.net进行微信公众号开发的例子好像比较少，这里做个笔记

　　首先，我们需要让微信能访问到我们的项目，所以要么需要有一个可以部署项目的连接到公网下的服务器，要么可以通过端口转发将请求转发到我们的项目，总之，就是要让微信服务器能访问到我们的项目。

　　另外，需要注意一下，微信回调通知的地址目前只支持80端口和443端口，所以一般的，我们都需要做个虚拟路径

　　其他的就不多说了，具体配置可以在微信公众号的开发文档中接入：https://developers.weixin.qq.com/doc/offiaccount/Basic_Information/Access_Overview.html

　　接入过程中会遇到很多坑，什么Url超时，Token验证错误等等，反正就是一些触不及防，当我们接入开发完后，发现我们使用的是明文传送，那当然就不行了，改成密文又要使用AES加密，反正接入不知道遇到多少坑

　　下面贴出我接入的代码，复制一下，稍稍修改就可以用了，可直接验证接入，支持明文密文传输：

　　一个加密解密辅助类：　　

using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;
using System.Xml;

namespace DemoApi
{
    public sealed class EncryptHelper
    {
        private EncryptHelper() { }

        /// <summary>
        /// Md5加密
        /// </summary>
        /// <param name="text"></param>
        /// <returns></returns>
        public static string Md5Encrypt(string text)
        {
            //MD5加密
            var md5 = MD5.Create();
            var bs = md5.ComputeHash(Encoding.UTF8.GetBytes(text));
            var sb = new StringBuilder();
            foreach (byte b in bs)
            {
                sb.Append(b.ToString("x2"));
            }
            //所有字符转为大写
            return sb.ToString().ToUpper();
        }
        /// <summary>
        /// HMAC-SHA1加密算法
        /// </summary>
        /// <param name="str">加密字符串</param>
        /// <returns></returns>
        public static string Sha1Encrypt(string str)
        {
            var sha1 = SHA1.Create();
            var hash = sha1.ComputeHash(Encoding.Default.GetBytes(str));
            //return BitConverter.ToString(hash).Replace("-", "");
            string byte2String = null;
            for (int i = 0; i < hash.Length; i++)
            {
                byte2String += hash[i].ToString("x2");
            }
            return byte2String;
        }
        /// <summary>
        /// AES加密 
        /// </summary>
        /// <param name="text">加密字符</param>
        /// <param name="encodingAESKey">加密的密码</param>
        /// <param name="appid">appId</param>
        /// <returns></returns>
        public static string AESEncrypt(string text, string encodingAESKey, string appid)
        {
            if (string.IsNullOrEmpty(text))
            {
                return text;
            }

            byte[] key;
            key = Convert.FromBase64String(encodingAESKey + "=");
            byte[] iv = new byte[16];
            Array.Copy(key, iv, 16);

            #region 生成随机值
            string codeSerial = "2,3,4,5,6,7,a,c,d,e,f,h,i,j,k,m,n,p,r,s,t,A,C,D,E,F,G,H,J,K,M,N,P,Q,R,S,U,V,W,X,Y,Z";
            string[] arr = codeSerial.Split(',');
            string code = "";
            int randValue = -1;
            Random rand = new Random(unchecked((int)DateTime.Now.Ticks));
            for (int i = 0; i < 16; i++)
            {
                randValue = rand.Next(0, arr.Length - 1);
                code += arr[randValue];
            }
            #endregion

            byte[] bRand = Encoding.UTF8.GetBytes(code);
            byte[] bAppid = Encoding.UTF8.GetBytes(appid);
            byte[] btmpMsg = Encoding.UTF8.GetBytes(text);

            int outval = 0, inval = btmpMsg.Length;
            for (int i = 0; i < 4; i++)
                outval = (outval << 8) + ((inval >> (i * 8)) & 255);

            byte[] bMsgLen = BitConverter.GetBytes(outval);
            byte[] bMsg = new byte[bRand.Length + bMsgLen.Length + bAppid.Length + btmpMsg.Length];

            Array.Copy(bRand, bMsg, bRand.Length);
            Array.Copy(bMsgLen, 0, bMsg, bRand.Length, bMsgLen.Length);
            Array.Copy(btmpMsg, 0, bMsg, bRand.Length + bMsgLen.Length, btmpMsg.Length);
            Array.Copy(bAppid, 0, bMsg, bRand.Length + bMsgLen.Length + btmpMsg.Length, bAppid.Length);

            var aes = new RijndaelManaged();
            //秘钥的大小，以位为单位
            aes.KeySize = 256;
            //支持的块大小
            aes.BlockSize = 128;
            //填充模式
            //aes.Padding = PaddingMode.PKCS7;
            aes.Padding = PaddingMode.None;
            aes.Mode = CipherMode.CBC;
            aes.Key = key;
            aes.IV = iv;
            var encrypt = aes.CreateEncryptor(aes.Key, aes.IV);
            byte[] xBuff = null;
            byte[] msg = new byte[bMsg.Length + 32 - bMsg.Length % 32];
            Array.Copy(bMsg, msg, bMsg.Length);

            #region 自己进行PKCS7补位，用系统自己带的不行，微信加密要使用这个
            int block_size = 32;
            // 计算需要填充的位数
            int amount_to_pad = block_size - (bMsg.Length % block_size);
            if (amount_to_pad == 0)
            {
                amount_to_pad = block_size;
            }
            // 获得补位所用的字符
            char pad_chr = (char)(byte)(amount_to_pad & 0xFF);
            string tmp = "";
            for (int index = 0; index < amount_to_pad; index++)
            {
                tmp += pad_chr;
            }
            byte[] pad = Encoding.UTF8.GetBytes(tmp);

            Array.Copy(pad, 0, msg, bMsg.Length, pad.Length);

            using (var ms = new MemoryStream())
            {
                using (var cs = new CryptoStream(ms, encrypt, CryptoStreamMode.Write))
                {
                    cs.Write(msg, 0, msg.Length);
                }
                xBuff = ms.ToArray();
            }
            #endregion

            #region 注释的也是一种方法，效果一样，微信加密不能使用这个！！！！
            //ICryptoTransform transform = aes.CreateEncryptor();
            //xBuff = transform.TransformFinalBlock(msg, 0, msg.Length);
            #endregion

            string output = Convert.ToBase64String(xBuff);
            return output;
        }
        /// <summary>
        /// AES解密
        /// </summary>
        /// <param name="encryptText">密文</param>
        /// <param name="encodingAESKey">秘钥</param>
        /// <param name="appid"></param>
        /// <returns></returns>
        public static string AESDecrypt(string encryptText, string encodingAESKey, out string appid)
        {
            if (string.IsNullOrEmpty(encryptText))
            {
                appid = "";
                return encryptText;
            }

            byte[] key;
            key = Convert.FromBase64String(encodingAESKey + "=");
            byte[] iv = new byte[16];
            Array.Copy(key, iv, 16);
            byte[] btmpMsg = null;

            RijndaelManaged aes = new RijndaelManaged();
            aes.KeySize = 256;
            aes.BlockSize = 128;
            aes.Mode = CipherMode.CBC;
            aes.Padding = PaddingMode.None;
            aes.Key = key;
            aes.IV = iv;
            var decrypt = aes.CreateDecryptor(aes.Key, aes.IV);
            using (var ms = new MemoryStream())
            {
                using (var cs = new CryptoStream(ms, decrypt, CryptoStreamMode.Write))
                {
                    byte[] xXml = Convert.FromBase64String(encryptText);
                    byte[] msg = new byte[xXml.Length + 32 - xXml.Length % 32];
                    Array.Copy(xXml, msg, xXml.Length);
                    cs.Write(xXml, 0, xXml.Length);
                }
                var decrypted = ms.ToArray();
                int pad = (int)decrypted[decrypted.Length - 1];
                if (pad < 1 || pad > 32)
                {
                    pad = 0;
                }
                btmpMsg = new byte[decrypted.Length - pad];
                Array.Copy(decrypted, 0, btmpMsg, 0, decrypted.Length - pad);
            }

            int len = BitConverter.ToInt32(btmpMsg, 16);
            len = IPAddress.NetworkToHostOrder(len);


            byte[] bMsg = new byte[len];
            byte[] bAppid = new byte[btmpMsg.Length - 20 - len];
            Array.Copy(btmpMsg, 20, bMsg, 0, len);
            Array.Copy(btmpMsg, 20 + len, bAppid, 0, btmpMsg.Length - 20 - len);
            string oriMsg = Encoding.UTF8.GetString(bMsg);
            appid = Encoding.UTF8.GetString(bAppid);
            return oriMsg;
        }
        /// <summary>
        /// AES解密
        /// </summary>
        /// <param name="encryptText">密文</param>
        /// <param name="encodingAESKey">秘钥</param>
        /// <param name="appid"></param>
        /// <returns></returns>
        public static string AESDecrypt(string encryptText, string encodingAESKey)
        {
            return AESDecrypt(encryptText, encodingAESKey, out _);
        }
    }

    public class CharSort : IComparer
    {
        public int Compare(object left, object right)
        {
            string sLeft = left as string;
            string sRight = right as string;
            int leftLength = sLeft.Length;
            int rightLength = sRight.Length;
            int index = 0;
            while (index < leftLength && index < rightLength)
            {
                if (sLeft[index] < sRight[index])
                    return -1;
                else if (sLeft[index] > sRight[index])
                    return 1;
                else
                    index++;
            }
            return leftLength - rightLength;
        }
    }
}

　　接入接口核心代码：　

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net.Http;
using System.Threading.Tasks;
using System.Web;
using System.Xml.Linq;
using Microsoft.AspNetCore.Mvc;

namespace DemoApi.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class WxController : ControllerBase
    {
        /// <summary>
        /// 生成签名
        /// </summary>
        /// <param name="args"></param>
        /// <returns></returns>
        [NonAction]
        private string MakeSign(params string[] args)
        {
            //字典排序
            Array.Sort(args);
            string tmpStr = string.Join("", args);
            //字符加密
            var sha1 = EncryptHelper.Sha1Encrypt(tmpStr);
            return sha1;
        }
        /// <summary>
        /// 生成消息签名
        /// </summary>
        /// <param name="args"></param>
        /// <returns></returns>
        [NonAction]
        private string MakeMsgSign(params string[] args)
        {
            //字典排序
            Array.Sort(args, new CharSort());
            string tmpStr = string.Join("", args);
            //字符加密
            var sha1 = EncryptHelper.Sha1Encrypt(tmpStr);
            return sha1;
        }
        /// <summary>
        /// 微信回调统一接口
        /// </summary>
        /// <returns></returns>
        [HttpGet, HttpPost]
        public string Service()
        {
            //获取配置文件中的数据
            var token = "";
            var encodingAESKey = "";
            var appId = "";

            bool isGet = string.Equals(HttpContext.Request.Method, HttpMethod.Get.Method, StringComparison.OrdinalIgnoreCase);
            bool isPost = string.Equals(HttpContext.Request.Method, HttpMethod.Post.Method, StringComparison.OrdinalIgnoreCase);
            if (!isGet && !isPost)
            {
                return "";
            }

            bool isEncrypt = false;
            try
            {
                var query = HttpContext.Request.QueryString.ToString();
                string msg_signature = "", nonce = "", timestamp = "", encrypt_type = "", signature = "", echostr = "";

                if (!string.IsNullOrEmpty(query))//需要验证签名
                {
                    var collection = HttpUtility.ParseQueryString(query);
                    msg_signature = collection["msg_signature"]?.Trim();
                    nonce = collection["nonce"]?.Trim();
                    timestamp = collection["timestamp"]?.Trim();
                    encrypt_type = collection["encrypt_type"]?.Trim();
                    signature = collection["signature"]?.Trim();
                    echostr = collection["echostr"]?.Trim();

                    if (!string.IsNullOrEmpty(encrypt_type))//有使用加密
                    {
                        if (!string.Equals(encrypt_type, "aes", StringComparison.OrdinalIgnoreCase))//只支持AES加密方式
                        {
                            return "";
                        }
                        isEncrypt = true;
                    }
                }

                //先验证签名
                if (!string.IsNullOrEmpty(signature))
                {
                    //字符加密
                    var sha1 = MakeSign(nonce, timestamp, token);
                    if (!sha1.Equals(signature, StringComparison.OrdinalIgnoreCase))//验证不通过
                    {
                        return "";
                    }

                    if (isGet)//是否Get请求，如果true,那么就认为是修改服务器回调配置信息
                    {
                        return echostr;
                    }
                }
                else
                {
                    return "";//没有签名，请求直接返回
                }

                var body = new StreamReader(HttpContext.Request.Body).ReadToEnd();

                if (isEncrypt)
                {
                    XDocument doc = XDocument.Parse(body);
                    var encrypt = doc.Element("xml").Element("Encrypt");

                    //验证消息签名
                    if (!string.IsNullOrEmpty(msg_signature))
                    {
                        //消息加密
                        var sha1 = MakeMsgSign(nonce, timestamp, encrypt.Value, token);
                        if (!sha1.Equals(msg_signature, StringComparison.OrdinalIgnoreCase))//验证不通过
                        {
                            return "";
                        }
                    }

                    body = EncryptHelper.AESDecrypt(encrypt.Value, encodingAESKey);//解密
                }

                if (!string.IsNullOrEmpty(body))
                {
                    //
                    //在这里根据body中的MsgType和Even来区分消息，然后来处理不同的业务逻辑
                    //
                    //

                    //result是上面逻辑处理完成之后的待返回结果，如返回文本消息：
                    var result = @"<xml>
                                      <ToUserName><![CDATA[toUser]]></ToUserName>
                                      <FromUserName><![CDATA[fromUser]]></FromUserName>
                                      <CreateTime>12345678</CreateTime>
                                      <MsgType><![CDATA[text]]></MsgType>
                                      <Content><![CDATA[你好]]></Content>
                                    </xml>";
                    if (!string.IsNullOrEmpty(result))
                    {
                        if (isEncrypt)
                        {
                            result = EncryptHelper.AESEncrypt(result, encodingAESKey, appId);
                            var _msg_signature = MakeMsgSign(nonce, timestamp, result, token);
                            result = $@"<xml>
                                                    <Encrypt><![CDATA[{result}]]></Encrypt>
                                                    <MsgSignature>{_msg_signature}</MsgSignature>
                                                    <TimeStamp>{timestamp}</TimeStamp>
                                                    <Nonce>{nonce}</Nonce>
                                                </xml>";
                        }
                        return result;
                    }

                    //如果这里我们的处理逻辑需要花费较长时间，可以这里先返回空(""),然后使用异步去处理业务逻辑，
                    //异步处理完后，调用微信的客服消息接口通知微信服务器
                }
            }
            catch (Exception ex)
            {
                //记录异常日志
            }

            return "";
        }

    }
}

　　如果只是接入，只需复制上面的接口代码，修改一下token,encodingAESKey,appId的值，然后使用接入的回调Url:http://XXX.XXXX.com/api/Wx就可以了

　　如果要处理微信通知过来的消息，可根据上面的接口自行处理业务逻辑，不过需要注意的是，微信回调接口只会等待5秒，5秒后断开，并重复3次，所以如果这里业务逻辑处理时间比较长的话，建议使用异步，在异步处理完之后，使用客服消息接口进行结果通知

　　另外开发过程中，可以使用微信公众平台接口调试工具进行调试：https://mp.weixin.qq.com/debug/cgi-bin/apiinfo?t=index

　　有一点注意一下，一般的，我们写接口时，为了保证接口返回的数据有一定格式，所以会写一些过滤器，对接口进行一个包装，比如我们会将结果包装成以下结构：　　

{
  "result": "success",
  "success": true,
  "error": null,
  "message": ""
}

 　　但是这个微信调用的接口不能包装，要返回微信指定的格式才行，这个切记！！！否则会返回Token验证失败的错误！