How does one configure HttpClient not to automatically redirect when it receives a 301 HTTP Status Code?

Question

Consider an ASP.NET Web API service that redirects

public class ThisController : ApiController
{
    /* more methods */

    public override HttpResponseMessage Post()
    {
        var result = new HttpResponseMessage(HttpStatusCode.MovedPermanently);
        // Post requests should be made to "ThatController" instead.
        string uri = Url.Route("That", null);
        result.Headers.Location = new Uri(uri, UriKind.Relative);
        return result;
    }
}

Trying to verify that POST'ing data to "api/this" will redirect you to "api/that", I have the following test method:

[TestMethod]
public void PostRedirects()
{
    using (var client = CreateHttpClient("application/json"))
    {
        var content = CreateContent(expected, "application/json");
        using (var responseMessage = client.PostAsync("api/this", content).Result)
        {
            Assert.AreEqual(HttpStatusCode.MovedPermanently, responseMessage.StatusCode);
            Assert.AreEqual(new Uri("https://api.example.com/api/that"), responseMessage.Headers.Location);
        }
    }
}

protected HttpClient CreateHttpClient(string mediaType)
{
    var client = new HttpClient();
    client.BaseAddress = new Uri("http://api.example.com/");
    MediaTypeWithQualityHeaderValue headerValue = MediaTypeWithQualityHeaderValue.Parse(mediaType);
    client.DefaultRequestHeaders.Accept.Add(headerValue);
    client.DefaultRequestHeaders.AcceptEncoding.Add(StringWithQualityHeaderValue.Parse("gzip"));
    client.DefaultRequestHeaders.AcceptEncoding.Add(StringWithQualityHeaderValue.Parse("deflate"));
    client.DefaultRequestHeaders.UserAgent.Add(new ProductInfoHeaderValue(new ProductHeaderValue("MyProduct", "1.0")));
    client.MaxResponseContentBufferSize = 1024*1024*8;
    return client;
}

protected ObjectContent CreateContent(T model, string mediaType)
{
    var requestMessage = new HttpRequestMessage();
    MediaTypeFormatter mediaTypeFormatter = null;
    switch (mediaType)
    {
        case "application/json":
            mediaTypeFormatter = new JsonMediaTypeFormatter();
            break;

        case "application/xml":
        case "text/xml":
            mediaTypeFormatter = new XmlMediaTypeFormatter();
            break;

        default:
            Assert.Fail();
            break;
    }

    return requestMessage.CreateContent(
        model,
        new[] { mediaTypeFormatter },
        new FormatterSelector());
}

What really happens that is that a HTTP Status Code is sent to the client with the correct Location header and that HttpClient then automatically performs a GET on that URI. As a result, my test never passes.

How do I configure the HttpClient not to automatically redirect when it receives a 301 so that I can verify that my server response?

Possible duplicate of How can I get System.Net.Http.HttpClient to not follow 302 redirects? — Michael Freidgeim
– Michael Freidgeim, Commented Mar 14, 2016 at 4:36

Mike Wasson · Accepted Answer · 2012-05-18 05:38:59Z

131

Try:

var handler = new HttpClientHandler() 
{
    AllowAutoRedirect = false
};

HttpClient client = new HttpClient(handler);

answered May 18, 2012 at 5:38

Mike Wasson

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4 Comments

Dai Over a year ago

Is it possible to do this on a per-request basis without needing two separate HttpClient instances (i.e. one that allows redirects and one that does not)?

Konstantin S. Over a year ago

Maybe you need this: handler.MaxAutomaticRedirections = 1

Todd Menier Over a year ago

@Dai No, that's not possible without reinventing the wheel unfortunately. But if you don't mind using a 3rd-party library that's exactly what I did in Flurl 3.0.

Vergil C. Over a year ago

Almost a decade later... how you can you set this up for a clean created using TestServer.CreateClient() ??

Todd · Accepted Answer · 2023-08-10 15:18:27Z

To clarify this issue. In client-side Blazor WASM the best you can do is cause the redirect to not happen, which may be good enough for your needs. In this case you will get back a status code of zero with no response headers, no response content, etc. It is NOT POSSIBLE to actually get the redirect status code (301, etc.), headers, etc. from the redirect response.

This is apparently due to the underlying JavaScript APIs used to implement HttpClientHandler:

How to get redirect url without following it using native fetch in JavaScript?

This makes coding an API client in browser hosted Blazor WebAssembly tricky if the API relies on redirect responses. You could probably eventually get it to work via user-facing navigation actions rather than HttpClient, but ugg.

Hope this saves someone some time.

Some references on the topic:

For anyone not running in a browser, here is a very nice example of doing this:

https://gist.github.com/Delaire/3f1283dc6365d705dfd6ba24498d4993

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