HttpClient返回错误代码500服务器内部错误

Question

这是拨打电话的方法：

public async System.Threading.Tasks.Task<Session> GetSessionFromLoginAsync()
 {
   try
      {
         var client = CustomHttpClient.GetClient();
         var httpRequest = PrepareRequest(_host, HttpMethod.Post, _connParameters);
            try
                {
                  var httpResponse = await client.SendAsync(httpRequest);
                     if (!httpResponse.IsSuccessStatusCode)
                      {
                        throw CustomException.CreateExceptionFromResponseErrors(httpResponse);
                      }

                      if (!httpResponse.IsSuccessStatusCode)
                      {
                        return null;
                      }

                   var headers = httpResponse.Headers.ToString();
                   string keyRoute = "ROUTEID=";
                   int posRouteID = headers.IndexOf(keyRoute);
                   string routeID2End = headers.Substring(posRouteID + keyRoute.Length, headers.Length - posRouteID - keyRoute.Length);
                   int semiColumn = routeID2End.IndexOf(";");
                   var routeID = ";" + keyRoute + routeID2End.Substring(0, semiColumn);
                   string dataResult = httpResponse.Content.ReadAsStringAsync().Result;
                   session = JsonConvert.DeserializeObject<SessionSL>(dataResult);
                   session.RouteID = routeID;
                    }
              catch (WebException ex)
                    {
                        var stream = ex.Response.GetResponseStream();
                        using (var sr = new StreamReader(stream))
                        {
                            Console.WriteLine(sr.ReadToEnd());
                        }
                    }
                }
                catch (Exception e)
                {
                    _esito = SendError(_esito, e, Constants.ErrorCode.LoginError);
                }


                return session;
            }

public static HttpRequestMessage PrepareRequest(string host, HttpMethod method, object contentObj)
        {

            var jsonObj = JsonConvert.SerializeObject(contentObj);

            ServicePointManager.ServerCertificateValidationCallback += delegate (object sender, X509Certificate cert,
                                                                               X509Chain chain,
                                                                               SslPolicyErrors sslPolicyErrors)
            { return true; };

            StringContent content = new StringContent(jsonObj.ToString(), Encoding.UTF8, "application/json");

            var HttpRequest = new HttpRequestMessage()
            {
                RequestUri = new Uri(host),
                Method = method,
                Content = content
            };

            return HttpRequest;

        }

这是CustomHttpClient类：

public sealed class CustomHttpClient
    {
        private static HttpClient _client;

        public static HttpClient GetClient()
        {
            if (_client == null)
            {
                var messageHandler = new HttpClientHandler()
                {
                    UseCookies = false,
            };

                //messageHandler.SslProtocols = SslProtocols.Tls12 | SslProtocols.Tls11 | SslProtocols.Tls;
                //messageHandler.ServerCertificateCustomValidationCallback = (message, cert, chain, errors) => true;
                ServicePointManager.ServerCertificateValidationCallback += delegate (object sender, X509Certificate cert,
                                                                               X509Chain chain,
                                                                               SslPolicyErrors sslPolicyErrors)
                { return true; };

                _client = new HttpClient(messageHandler)
                {
                    Timeout = TimeSpan.FromSeconds(Constants._HTTP_TIMEOUT_SEC),
                    //BaseAddress = new Uri("myendpoint");
                };
                _client.DefaultRequestHeaders.Accept.Clear();
                _client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
                _client.DefaultRequestHeaders.Add("Connection", "keep-alive");
            }

            return _client;
        }
    }

我的应用是世界粮食计划署... 我不明白的是，我使用Xamarin Forms制作应用程序时使用的相同方法，但从未在响应中收到错误HTTP 500 ... 而且我认为代码中没有错误..即使在服务器上也没有错误，因为使用Postman之类的工具，我可以轻松连接，并且总是收到消息“ 200 OK” ...