.Net HttpWebRequest.GetResponse() raises exception when http status code 400 (bad request) is returned

Question

I am in a situation where when I get an HTTP 400 code from the server, it is a completely legal way of the server telling me what was wrong with my request (using a message in the HTTP response content)

However, the .NET HttpWebRequest raises an exception when the status code is 400.

How do I handle this? For me a 400 is completely legal, and rather helpful. The HTTP content has some important information but the exception throws me off my path.

Answer 1

It would be nice if there were some way of turning off "throw on non-success code" but if you catch WebException you can at least use the response:

using System;
using System.IO;
using System.Web;
using System.Net;

public class Test
{
    static void Main()
    {
        WebRequest request = WebRequest.Create("http://csharpindepth.com/asd");
        try
        {
            using (WebResponse response = request.GetResponse())
            {
                Console.WriteLine("Won't get here");
            }
        }
        catch (WebException e)
        {
            using (WebResponse response = e.Response)
            {
                HttpWebResponse httpResponse = (HttpWebResponse) response;
                Console.WriteLine("Error code: {0}", httpResponse.StatusCode);
                using (Stream data = response.GetResponseStream())
                {
                    string text = new StreamReader(data).ReadToEnd();
                    Console.WriteLine(text);
                }
            }
        }
    }
}

You might like to encapsulate the "get me a response even if it's not a success code" bit in a separate method. (I'd suggest you still throw if there isn't a response, e.g. if you couldn't connect.)

Answer 2

Interestingly, the HttpWebResponse.GetResponseStream() that you get from the WebException.Response is not the same as the response stream that you would have received from server. In our environment, we're losing actual server responses when a 400 HTTP status code is returned back to the client using the HttpWebRequest/HttpWebResponse objects. From what we've seen, the response stream associated with the WebException's HttpWebResponse is generated at the client and does not include any of the response body from the server. Very frustrating, as we want to message back to the client the reason for the bad request.