webclient and expect100continue

Question

What is the best way to set expect100continue when using WebClient(C#.NET). I have this code below, I still see 100 continue in the header. Stupid apache still complains with 505 error.

        string url = "http://aaaa.com";
        ServicePointManager.Expect100Continue = false;

        WebClient service = new WebClient();           
        service.Credentials = new NetworkCredential("username", "password");
        service.Headers.Add("Content-Type","text/xml");

        service.UploadStringCompleted += (sender, e) => CompleteCallback(BuildResponse(e));
        service.UploadStringAsync(new Uri(url), "POST", query);

Note: If I put the above in a console app and let it run - then I do not see the headers in fiddler. But, my code is embedded in a user library which is loaded by a WPF app. So, Is there more to Expect100Continue in terms of thread, initialization, etc. Now, I think it is more of my code issue.

Answer 1

You need to set the Expect100Continue property on the ServicePoint used for the URI you're accessing:

var uri = new Uri("http://foo.bar.baz");
var servicePoint = ServicePointManager.FindServicePoint(uri);
servicePoint.Expect100Continue = false;

Answer 2

The only way to do this is to create an override.

   public class ExpectContinueAware : System.Net.WebClient
    {
        protected override System.Net.WebRequest GetWebRequest(Uri address)
        {
            System.Net.WebRequest request = base.GetWebRequest(address);
            if (request is System.Net.HttpWebRequest)
            {
                var hwr = request as System.Net.HttpWebRequest;
                hwr.ServicePoint.Expect100Continue = false;
            }
            return request;
        }
    }

This works perfect.