C# HttpClient not sending basic authentication after redirect

问题

My code is making an HTTP GET to a web service URL that requires basic authentication.

I've implemented this using an HttpClient with an HttpClientHandler that has the Credentials property defined.

This all works perfectly.. Except for one of my use-cases where I'm making the authenticated GET to: http://somedomain.com which redirects to http://www.somedomain.com.

It seems that the HttpClientHandler clears the authentication header during the redirect. How can I prevent this? I want the credentials to be sent regardless of redirects.

This is my code:

// prepare the request
var request = new HttpRequestMessage(method, url);
using (var handler = new HttpClientHandler { Credentials = new NetworkCredential(username, password) , PreAuthenticate = true })
using (var client = new HttpClient(handler))
{
    // send the request
    var response = await client.SendAsync(request);

Note: this is a related question: Keeping HTTP Basic Authentification alive while being redirected But since I'm using different classes for making the request, there might be a better, more specific solution

回答1:

The default HttpClientHandler uses the same HttpWebRequest infrastructure under the covers. Instead of assigning a NetworkCredential to the Credentials property, create a CredentialCache and assign that.

This is what I use in place of the AutoRedirect and with a little async/await fairy dust it would probably be a whole lot prettier and more reliable.

 public class GlobalRedirectHandler : DelegatingHandler {

    protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) {
        var tcs = new TaskCompletionSource<HttpResponseMessage>();

        base.SendAsync(request, cancellationToken)
            .ContinueWith(t => {
                HttpResponseMessage response;
                try {
                    response = t.Result;
                }
                catch (Exception e) {
                    response = new HttpResponseMessage(HttpStatusCode.ServiceUnavailable);
                    response.ReasonPhrase = e.Message;
                }
                if (response.StatusCode == HttpStatusCode.MovedPermanently
                    || response.StatusCode == HttpStatusCode.Moved
                    || response.StatusCode == HttpStatusCode.Redirect
                    || response.StatusCode == HttpStatusCode.Found
                    || response.StatusCode == HttpStatusCode.SeeOther
                    || response.StatusCode == HttpStatusCode.RedirectKeepVerb
                    || response.StatusCode == HttpStatusCode.TemporaryRedirect

                    || (int)response.StatusCode == 308) 
                {

                    var newRequest = CopyRequest(response.RequestMessage);

                    if (response.StatusCode == HttpStatusCode.Redirect 
                        || response.StatusCode == HttpStatusCode.Found
                        || response.StatusCode == HttpStatusCode.SeeOther)
                    {
                        newRequest.Content = null;
                        newRequest.Method = HttpMethod.Get;

                    }
                    newRequest.RequestUri = response.Headers.Location;

                    base.SendAsync(newRequest, cancellationToken)
                        .ContinueWith(t2 => tcs.SetResult(t2.Result));
                }
                else {
                    tcs.SetResult(response);
                }
            });

        return tcs.Task;
    }

    private static HttpRequestMessage CopyRequest(HttpRequestMessage oldRequest) {
        var newrequest = new HttpRequestMessage(oldRequest.Method, oldRequest.RequestUri);

        foreach (var header in oldRequest.Headers) {
            newrequest.Headers.TryAddWithoutValidation(header.Key, header.Value);
        }
        foreach (var property in oldRequest.Properties) {
            newrequest.Properties.Add(property);
        }
        if (oldRequest.Content != null) newrequest.Content = new StreamContent(oldRequest.Content.ReadAsStreamAsync().Result);
        return newrequest;
    }
}

来源：https://stackoverflow.com/questions/19491525/c-sharp-httpclient-not-sending-basic-authentication-after-redirect