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I have a project that is communicating with a backend java server (REST) for all related business operations. I am using HttpClient to send my requests. My problem lies in this: If a request fails, ie an AggregateException is raised from the .Result with 'a task was cancelled' in almost all the rest calls to the server my HttpClient instance loses the Accept and Accept-Language DefaultRequestHeaders. I have tried many different variations in the way I am instantiating the client, either as a static class or through the webconfig but it happens in all cases and i have no ideas left. Please see code below. I load from my web.Config the properties and this is my object which gets filled out correctly (got it from here): 

public sealed class AthenaHttpClients : ConfigurationSection
{
    private HttpClient _client { get; set; }
    [ConfigurationProperty("athenaFactoryClient", IsRequired = true)]
    public AthenaFactoryHttpClient FactoryClient
    {
        get { return (AthenaFactoryHttpClient)base["athenaFactoryClient"]; }
        set { base["athenaFactoryClient"] = value; }
    }

    private static AthenaHttpClients instance = null;

    public static HttpClient GetClient()
    {
        if (instance == null)
        {
            instance = (AthenaHttpClients)WebConfigurationManager.GetSection("athenaHttpClients");
        }

        instance.FactoryClient.Client = HttpClientFactory.Create(new CustomDelegatingHandlerTokenRefresher());
        instance.FactoryClient.Client.BaseAddress = new Uri(ConfigurationManager.AppSettings["uri"]);
        instance.FactoryClient.Client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue(instance.FactoryClient.HeaderValue));
        instance.FactoryClient.Client.DefaultRequestHeaders.AcceptLanguage.Add(new StringWithQualityHeaderValue(instance.FactoryClient.Language));
        instance.FactoryClient.Client.DefaultRequestHeaders.Remove("Authorization");

        return instance.FactoryClient.Client;
    }
}
public class AthenaFactoryHttpClient : ConfigurationElement
{
    [ConfigurationProperty("headerValue", IsRequired = true)]
    public string HeaderValue
    {
        get { return (string)base["headerValue"]; }
        set { base["headerValue"] = value; }
    }

    [ConfigurationProperty("language", IsRequired = true)]
    public string Language
    {
        get { return (string)base["language"]; }
        set { base["language"] = value; }
    }
    public HttpClient Client { get; set; }
}

}

I am calling my client like this:

private HttpClient client = AthenaHttpClients.GetClient();

and this is one of my calls to the backend server:

internal HttpResponseMessage getStudyContract(string id)
    {
        try
        {
            client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", (string)HttpContext.Current.Session["accessToken"]);
            HttpResponseMessage response = client.GetAsync(restEndpoint + restStudyContractsEndpoint + "/" + id).Result;
            return response;
        }
        catch (AggregateException ex)
        {
            throw new RestHttpClientRequestException(restRequestExceptionMessage, ex.StackTrace);
        }
        catch (Exception ex)
        {
            throw new RestHttpClientRequestException(ex.Message, ex.StackTrace);
        }
    }

(I know it's not the best implementation using the async methods with the .Result, but for now it is ok). I force my request to getStudyContract() to fail by sending an Id with empty string. I then get the AggregateException and then all subsequent calls to my client simply lose the Accept and Accept-Language. I don't know what I am doing wrong. If anyone has a suggestion, please help!

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  • Are there any other exceptions in the `InnerExceptions` collection in the `AggregateException` that is thrown? – CodingGorilla Mar 07 '16 at 19:12
  • No there aren't any other, since I force the 'task cancelled' exception by posting to invalid url (no Id). – maria Mar 08 '16 at 08:50
  • Posting to an invalid url should not force the task to cancel, it should return an error. The only thing that should cause the task to cancel is either you requesting a cancel (via a `CanellationTokenSource`) or the process shutting down or something like that. Seems like there is something else going on here. – CodingGorilla Mar 08 '16 at 13:29
  • My delegating Hanlder indeed has a CancellationToken but I haven't set anything specific " protected override Task SendAsync( HttpRequestMessage request, CancellationToken cancellationToken){ var response = base.SendAsync(request, cancellationToken); return response; } However, is it reasonable to lose the headers? Should I do something with the CancellationToken? I wans't focusing on that at all because I am forcing this exception – maria Mar 08 '16 at 14:54
  • What I am basically saying is that, the headers are missing when an unhandled exception takes place, and i am creating this, maybe mistakenly through the invalid request. The result is the same either from the task cancelled, or from any other unhandled exception – maria Mar 08 '16 at 15:05

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