internal static HttpClient CreateClientwithHeaders()
        {
            var handler = new HttpClientHandler()
            {
                Credentials = CredentialCache.DefaultNetworkCredentials
            };
            return new HttpClient(handler);
        }

        internal static HttpClient CreateClient()
        {
            var client = CreateClientwithHeaders();
            return client;
        }
        internal static async Task<string> PostPdf<DocInput>(DocInput card, string urlAction)
        {
            using (var client = CreateClient())
            {
                try
                {
                    client.Timeout = TimeSpan.FromMinutes(2);
                    HttpContent httpContent = new StringContent(JsonConvert.SerializeObject(card), Encoding.UTF8);
                    httpContent.Headers.ContentType = new MediaTypeHeaderValue("application/json");
                    
                    HttpResponseMessage response = await client.PostAsync(new Uri(urlAction), httpContent);
                    if (!response.IsSuccessStatusCode)
                    {
                        return response.Content.ReadAsStringAsync().Result;
                    }
                    return await response.Content.ReadAsStringAsync();

                }
                catch (Exception ex)
                {
                    DocResult dr = new DocResult();
                    dr.error_text = $"Ошибка в PostPdf: err={ex.Message} {ex.InnerException}, urlAction={urlAction}";
                    dr.success = false;
                    dr.result_text = "Error";
                    return JsonConvert.SerializeObject(dr);
                }

            }
        }