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

User · Answer

Try this  it s VB-Code  -    Try  Catch exp As WebException   Dim sResponse As String   New StreamReader exp Response GetResponseStream    ReadToEnd End Try

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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

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This solved it for me  https   gist github com beccasaurus 929007 a8f820b153a1cfdee3d06a9c0a1d7ebfced8bb77  TL DR  Problem  localhost returns expected content  remote IP alters 400 content to  Bad Request  Solution  Adding  lt httpErrors existingResponse  PassThrough  gt  lt  httpErrors gt  to web config configuration system webServer solved this for me  now all servers  local  amp  remote  return the exact same content  generated by me  regardless of the IP address and or HTTP code I return

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I had similar issues when trying to connect to Google s OAuth2 service    I ended up writing the POST manually  not using WebRequest  like this   TcpClient client   new TcpClient  accounts google com   443   Stream netStream   client GetStream    SslStream sslStream   new SslStream netStream   sslStream AuthenticateAsClient  accounts google com           byte   contentAsBytes   Encoding ASCII GetBytes content ToString          StringBuilder msg   new StringBuilder        msg AppendLine  POST  o oauth2 token HTTP 1 1        msg AppendLine  Host  accounts google com        msg AppendLine  Content-Type  application x-www-form-urlencoded        msg AppendLine  Content-Length      contentAsBytes Length ToString         msg AppendLine          Debug WriteLine  Request        Debug WriteLine msg ToString         Debug WriteLine content ToString          byte   headerAsBytes   Encoding ASCII GetBytes msg ToString         sslStream Write headerAsBytes       sslStream Write contentAsBytes      Debug WriteLine  Response     StreamReader reader   new StreamReader sslStream   while  true        Print the response line by line to the debug stream for inspection      string line   reader ReadLine        if  line    null  break      Debug WriteLine line       The response that gets written to the response stream contains the specific error text that you re after   In particular  my problem was that I was putting endlines between url-encoded data pieces  When I took them out  everything worked  You might be able to use a similar technique to connect to your service and read the actual response error text

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An asynchronous version of extension function       public static async Task lt WebResponse gt  GetResponseAsyncNoEx this WebRequest request                try                       return await request GetResponseAsync                      catch WebException ex                        return ex Response

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I know this has already been answered a long time ago  but I made an extension method to hopefully help other people that come to this question   Code   public static class WebRequestExtensions       public static WebResponse GetResponseWithoutException this WebRequest request                if  request    null                        throw new ArgumentNullException  request                       try                       return request GetResponse                      catch  WebException e                        if  e Response    null                                throw                             return e Response                      Usage   var request    HttpWebRequest WebRequest CreateHttp  http   invalidurl com            initialize more fields   using  var response    HttpWebResponse request GetResponseWithoutException          Console WriteLine  I got Http Status Code   0    response StatusCode

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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                    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

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

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