var client = new FhirClient("http://testserv.ru/service/api/fhir/");
            client.OnBeforeRequest += (object sl, BeforeRequestEventArgs e1) =>
            {
                e1.RawRequest.Headers.Add("authorization", Guid);
                e1.RawRequest.ContentType = "application/json";
            };

            client.PreferredFormat = ResourceFormat.Json;
            client.UseFormatParam = false;
            client.ReturnFullResource = false;
            client.Timeout = 60000;

client.Get("http://testserv.ru/service/api/fhir/Patient/a6bfef9f-fd80-4c7b-b6c2-5c55ed842e6b");

System.Net.ProtocolViolationException: Недопустимое значение строки даты в верхнем колонтитуле.
   в System.Net.HttpProtocolUtils.string2date(String S)
   в System.Net.HttpWebResponse.get_LastModified()
   в Hl7.Fhir.Rest.HttpToEntryExtensions.ToBundleEntry(HttpWebResponse response, Byte[] body) в C:\Git\fhir-net-api\src\Hl7.Fhir.Core\Rest\HttpToEntryExtensions.cs:строка 37
   в Hl7.Fhir.Rest.Requester.doRequest(EntryComponent interaction) в C:\Git\fhir-net-api\src\Hl7.Fhir.Core\Rest\Requester.cs:строка 119
   в Hl7.Fhir.Rest.Requester.Execute(EntryComponent interaction) в C:\Git\fhir-net-api\src\Hl7.Fhir.Core\Rest\Requester.cs:строка 58
   в Hl7.Fhir.Rest.FhirClient.execute[TResource](Bundle tx, IEnumerable`1 expect) в C:\Git\fhir-net-api\src\Hl7.Fhir.Core\Rest\FhirClient.cs:строка 807
   в Hl7.Fhir.Rest.FhirClient.execute[TResource](Bundle tx, HttpStatusCode expect) в C:\Git\fhir-net-api\src\Hl7.Fhir.Core\Rest\FhirClient.cs:строка 799
   в Hl7.Fhir.Rest.FhirClient.Get(Uri url) в C:\Git\fhir-net-api\src\Hl7.Fhir.Core\Rest\FhirClient.cs:строка 561
   в Hl7.Fhir.Rest.FhirClient.Get(String url) в C:\Git\fhir-net-api\src\Hl7.Fhir.Core\Rest\FhirClient.cs:строка 577
   в ODLI_service.Frmmain.bTestconnection_Click(Object sender, EventArgs e) в c:\ПО\test\test_service\Form1.cs:строка 344

HTTP/1.1 200 OK
Date: Fri, 21 Dec 2018 21:02:50 GMT
Content-Type: application/json; charset=utf-8
Connection: keep-alive
Last-Modified: 21.12.18 19:31:08 +00:00
ETag: v18c1f0d-efc2-4f2c-890d-3780ca17dcad
Server: n3.gw
Content-Length: 1252