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 (if there is one):

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)             {                 // TODO: Handle response being null                 HttpWebResponse httpResponse = (HttpWebResponse) response;                 Console.WriteLine("Error code: {0}", httpResponse.StatusCode);                 using (Stream data = response.GetResponseStream())                 using (var reader = new StreamReader(data))                 {                     string text = reader.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.)

If the error response may be large (which is unusual) you may want to tweak HttpWebRequest.DefaultMaximumErrorResponseLength to make sure you get the whole error.