public static IDictionary<string, object> DecodeJWT(string jwttoken,string key)

        {

            //从/.well-known/openid-configuration路径获取jwks_uri

            var webClient = new WebClient();

            var endpoint = "http://localhost:5000/.well-known/openid-configuration";

            var json = webClient.DownloadString(endpoint);

            JObject metadata = JsonConvert.DeserializeObject<JObject>(json);

            var jwksUri = metadata["jwks_uri"].ToString();

            //从jwks_uri获取keys

            json = webClient.DownloadString(jwksUri);

            var keys = JsonConvert.DeserializeObject<CustomJWKs>(json);

            //从jwt获取头部kid,并从keys中找到匹配kid的key

            string[] tokenParts = jwttoken.Split('.');

            byte[] bytes = FromBase64Url(tokenParts[]);

            string head= Encoding.UTF8.GetString(bytes);

            string kid = JsonConvert.DeserializeObject<JObject>(head)["kid"].ToString();

            var defaultkey=keys.keys.Where(t => t.kid == kid).FirstOrDefault();

            if(defaultkey==null)

            {

                throw new Exception("未找到匹配的kid");

            }

            //jwt解密

            return RS256Decode(jwttoken, key, defaultkey.e, defaultkey.n);

        }

         public static IDictionary<string, object> RS256Decode(string token, string secret, string exponent,string modulus)

        {

            try

            {

                IJsonSerializer serializer = new JsonNetSerializer();

                IDateTimeProvider provider = new UtcDateTimeProvider();

                IJwtValidator validator = new JwtValidator(serializer, provider);

                IBase64UrlEncoder urlEncoder = new JwtBase64UrlEncoder();

                RSAlgorithmFactory rS256Algorithm = new RSAlgorithmFactory(() =>

                {

                    RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();

                    rsa.ImportParameters(

                      new RSAParameters()

                      {

                          Modulus = FromBase64Url(modulus),

                          Exponent = FromBase64Url(exponent)

                      });

                    byte[] rsaBytes = rsa.ExportCspBlob(true);

                    X509Certificate2 cert = new X509Certificate2(rsaBytes);

                    return cert;

                });

                IJwtDecoder decoder = new JwtDecoder(serializer, validator, urlEncoder, rS256Algorithm);

                var json = decoder.DecodeToObject(token, secret, verify: false);

                return json;

            }

            catch (TokenExpiredException)

            {

                throw new Exception("token已过期");

                //Console.WriteLine("Token has expired");

                //return null;

            }

            catch (SignatureVerificationException)

            {

                throw new Exception("token验证失败");

                //Console.WriteLine("Token has invalid signature");

                //return null;

            }

        }

        public static byte[] FromBase64Url(string base64Url)

        {

            string padded = base64Url.Length %  ==

                ? base64Url : base64Url + "====".Substring(base64Url.Length % );

            string base64 = padded.Replace("_", "/")

                                  .Replace("-", "+");

            return Convert.FromBase64String(base64);

        }