I wrote the following program in C# using .NET 4.7.1:
var req = (HttpWebRequest) WebRequest.Create(myUrl); req.AllowAutoRedirect = false; var rsp = req.GetResponse(); Console.WriteLine(rsp.Headers["Location"]); The site I am requesting from is returning a 301 response, and the "Location" header contains the URL to redirect to.
If I do the exact same thing using .NET Core 2.1, I will instead get a WebException thrown from the call to GetResponse. How can I avoid this?
Based on this, you need to trap it in try/catch block and inspect the WebException:
If you set
AllowAutoRedirect, then you will end up not following the redirect. That means ending up with the 301 response.HttpWebRequest(unlikeHttpClient) throws exceptions for non-successful (non-200) status codes. So, getting an exception (most likely aWebException) is expected. So, if you need to handle that redirect (which is HTTPS -> HTTP by the way), you need to trap it in try/catch block and inspect the WebException etc. That is standard use ofHttpWebRequest.That is why we recommend devs use
HttpClientwhich has an easier use pattern.
Something like this:
WebResponse rsp; try { rsp = req.GetResponse(); } catch(WebException ex) { if(ex.Message.Contains("301")) rsp = ex.Result; } I pretty much figured it out while I was working on it, but I thought I'd post it here in case others run into the same issue.
The response is included as part of the exception that is throw, so I was able to get the same behavior as in .NET 4.7.1 by modifying my code to this:
var req = (HttpWebRequest) WebRequest.Create(myUrl); req.AllowAutoRedirect = false; try { var rsp = req.GetResponse(); Console.WriteLine(rsp.Headers["Location"]); } catch (WebException e) { var rsp = (HttpWebResponse) e.Response; if (rsp.StatusCode == HttpStatusCode.Moved || rsp.StatusCode == HttpStatusCode.MovedPermanently || rsp.StatusCode == HttpStatusCode.Found) { Console.WriteLine(rsp.Headers["Location"]); } else throw; } 
var response=await httpClient.GetAsync(...); response.Headers.Location ...