asp.net core 造一个微信小程序OAuth服务（SDK）

具体的授权认证在微信小程序的官方文档，偷个懒，就不写了

推荐一个好用的http请求类库

$ install-package Flurl 
$ install-package Flurl.Http

• 链式的http请求方式，可以说比前端的axios.js更好用
• 入门基础可以百度到的，就不过多介绍了

定义一个微信小程序Exception

    public class WeixinMiniProgramExcption:Exception
    {
        public WeixinMiniProgramExcption(string message):base(message)
        {

        }
        //props...
    }

定义一个文件配置实体类

    public class WeixinMiniProgramOptions:IOptions<WeixinMiniProgramOptions>
    {
        public string AppId { get; set; } //小程序的AppId 
        public string AppSecret { get; set; } //小程序的AppSecret

        public WeixinMiniProgramOptions Value => this;
    }

定义一个小程序用户实体类 接下来会用到

   public class WeixinUserInfo
    {
        public string OpenId { get; set; }

        [JsonProperty("session_key")]
        public string SessionKey { get; set; }

        public string UnionId { get; set; }

        public int ErrCode { get; set; }

        public string ErrMsg { get; set; }
    }

服务类 ，直接开搞，请看注释

   public class WeixinMiniProgramOAuthService
    {
        //使用控制反转的方式
        private readonly WeixinMiniProgramOptions _options;
        //一开始说的Flurl 客户端，在构造函数初始化，规范点
        private readonly IFlurlClient _client;

        public WeixinMiniProgramOAuthService(IOptions<WeixinMiniProgramOptions> options)
        {
            _options = options.Value;
            //使用 baseUrl 这个构造函数
            _client = new FlurlClient("https://api.weixin.qq.com");
        }
        public async Task<WeixinUserInfo> AuthorizationCodeAsync(string code)
        {
           //这就是Flurl的好用之处
            var data = await _client.Request("/sns/jscode2session")
                                  .SetQueryParam("appid", _options.AppId)
                                  .SetQueryParam("secret", _options.AppSecret)
                                  .SetQueryParam("js_code", code)
                                  .SetQueryParam("grant_type", "authorization_code")
                                  .GetJsonAsync<WeixinUserInfo>();
            //抛异常的好处是快速定位到bug，方便后续扩展操作
            if (data.ErrCode != 0) 
                throw new WeixinMiniProgramExcption(data.ErrMsg);
            return data;
        }
      //校验签名的方法
        public static bool ValidateSignature(string sessionKey, string rawData, string signature)
        {
            var str = rawData + sessionKey;
            var utf8Bytes = Encoding.UTF8.GetBytes(str);
            var hash = SHA1.Create().ComputeHash(utf8Bytes);
            var bit = BitConverter.ToString(hash);
            var result = bit.Replace("-", "");
            return string.Equals(signature, result, StringComparison.OrdinalIgnoreCase);
        }
        //解密前端数据的方法
        public static JObject DecryptData(string sessionKey, string iv, string encryptedData)
        {
            var encryptedBytes = Convert.FromBase64String(encryptedData);
            using var rij = Rijndael.Create();
            rij.KeySize = 128;
            rij.Key = Convert.FromBase64String(sessionKey);
            rij.IV = Convert.FromBase64String(iv);
            rij.Mode = CipherMode.CBC;
            rij.Padding = PaddingMode.PKCS7;
            using var decryptor = rij.CreateDecryptor();
            var json = Encoding.UTF8.GetString(decryptor.TransformFinalBlock(encryptedBytes, 0, encryptedBytes.Length));
            return JObject.Parse(json);
        }
        //解密服务的入口
        public async Task<JObject> Decoder(string jsCode,string iv,string encryptedData)
        {
            var code = await AuthorizationCodeAsync(jsCode);

            var info = DecryptData(code.SessionKey, iv, encryptedData);
            return info;
        }
    }

• 用JObject作为返回类型的原因：解密的数据格式是动态的

来个 webapi程序试试

appsettings.json

{
 "MiniProgram": {
    "AppId": "你的appid",
    "AppSecret": "你的secret"
  }
}

依赖注入

  public void ConfigureServices(IServiceCollection services)
  {
     services.Configure<WeixinMiniProgramOptions>(Configuration.GetSection("MiniProgram"));
     services.AddSingleton<WeixinMiniProgramOAuthService>();
  }

搞个控制器试试

• 记得要跟小程序开发一起调试

    [Route("api/[controller]")]
    [ApiController]
    public class ValuesController : ControllerBase
    {
        private readonly WeixinMiniProgramOAuthService _service;

        public ValuesController(WeixinMiniProgramOAuthService service)
        {
            _service = service;
        }
        [HttpPost]
        public async Task<ActionResult> WeixinDecoder([FromBody]DecodeVM vm)
        {
            var data = await _service.Decoder(vm.Iv, vm.JsCode, vm.EncryptedData);
            return Ok(data);
        }
    }
    public class DecodeVM
    {
        public string JsCode { get; set; }
        public string Iv { get; set; }
        public string EncryptedData { get; set; }
    }