HttpClient strange behavior when trying to access WCF Rest service with Windows Auth

Question

I am creating a client-server application using WCF REST services (.Net 4.0) and I see really strange error there. To access the service I use HttpClient class, the code looks like:

public TResponse Post<TRequest, TResponse>(Uri uri, TRequest request)
    using (HttpClient client = new HttpClient())
    {                
        client.TransportSettings.Credentials = CredentialCache.DefaultCredentials;
        client.TransportSettings.ConnectionTimeout = TimeSpan.FromSeconds(200);

        using (HttpResponseMessage response = client.Post(uri, HttpContentExtensions.CreateDataContract(request, null)))
        {
            response.EnsureStatusIsSuccessful();
            return response.Content.ReadAsDataContract<TResponse>();
        }
    }
}

I host my service on IIS7 and when anonymous auth is enabled everything works well, but when I turn on windows auth some random requests (in average 1 of 10) get failed with 400-Bad request status and error message is : Bad Request - Invalid Verb. HTTP Error 400. The request verb is invalid.

What could it be?

And a little update: if fiddler is turned on everything works perfect.

Can you validate that the Identity Account running the Application Pool has access to look up users/groups? — Caleb Keith
– Caleb Keith, Commented Dec 18, 2012 at 14:27

John Newman · Accepted Answer · 2014-07-11 17:15:09Z

1

I just ran into the same thing here. Quite a mystery really. I don't understand why having fiddler running removes the problem.

I eventually found that the issue was caused the by the "expect continue" header being added to the post. I removed that and the post succeeds instead of the 400 bad request.

Here's a good entry about it: http://blogs.msdn.com/b/jaskis/archive/2009/04/19/asmx-post-request-fails-with-http-400-error-when-content-length-size-increases.aspx

In my case this was apache HTTP Client v4.0 so,

    httpClient.getParams().setBooleanParameter(
            CoreProtocolPNames.USE_EXPECT_CONTINUE, false);

did the trick.

answered Jul 11, 2014 at 17:15

John Newman

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