How to get error information when HttpWebRequest GetResponse fails

Question

I am initiating an HttpWebRequest and then retrieving it s response   Occasionally  I get a 500  or at least 5    error  but no description   I have control over both endpoints and would like the receiving end to get a little bit more information   For example  I would like to pass the exception message from server to client   Is this possible using HttpWebRequest and HttpWebResponse   Code   try       HttpWebRequest webRequest   HttpWebRequest Create URL  as HttpWebRequest      webRequest Method   WebRequestMethods Http Get      webRequest Credentials   new NetworkCredential Username  Password       webRequest ContentType    application x-www-form-urlencoded       using HttpWebResponse response   webRequest GetResponse   as HttpWebResponse                if response StatusCode    HttpStatusCode OK                           Do stuff with response GetResponseStream                      catch Exception ex        ShowError ex          if the server returns a 500 error than the webRequest GetResponse   method        throws an exception and all I get is  The remote server returned an error   500        Any help with this would be much appreciated

User · Answer

I came across this question when trying to check if a file existed on an FTP site or not. If the file doesn't exist there will be an error when trying to check its timestamp. But I want to make sure the error is not something else, by checking its type.

The Response property on WebException will be of type FtpWebResponse on which you can check its StatusCode property to see which FTP error you have.

Here's the code I ended up with:

    public static bool FileExists(string host, string username, string password, string filename)
    {
        // create FTP request
        FtpWebRequest request = (FtpWebRequest)WebRequest.Create("ftp://" + host + "/" + filename);
        request.Credentials = new NetworkCredential(username, password);

        // we want to get date stamp - to see if the file exists
        request.Method = WebRequestMethods.Ftp.GetDateTimestamp;

        try
        {
            FtpWebResponse response = (FtpWebResponse)request.GetResponse();
            var lastModified = response.LastModified;

            // if we get the last modified date then the file exists
            return true;
        }
        catch (WebException ex)
        {
            var ftpResponse = (FtpWebResponse)ex.Response;

            // if the status code is 'file unavailable' then the file doesn't exist
            // may be different depending upon FTP server software
            if (ftpResponse.StatusCode == FtpStatusCode.ActionNotTakenFileUnavailable)
            {
                return false;
            }

            // some other error - like maybe internet is down
            throw;
        }
    }

User · Answer

I faced a similar situation   I was trying to read raw response in case of an HTTP error consuming a SOAP service  using BasicHTTPBinding   However  when reading the response using GetResponseStream    got the error      Stream not readable   So  this code worked for me   try       response   basicHTTPBindingClient CallOperation request     catch  ProtocolException exception        var webException   exception InnerException as WebException      var rawResponse   string Empty       var alreadyClosedStream   webException Response GetResponseStream   as MemoryStream      using  var brandNewStream   new MemoryStream alreadyClosedStream ToArray         using  var reader   new StreamReader brandNewStream           rawResponse   reader ReadToEnd

User · Answer

You can also use this library which wraps HttpWebRequest and Response into simple methods that return objects based on the results   It uses some of the techniques described in these answers and has plenty of code inspired by answers from this and similar threads   It automatically catches any exceptions  seeks to abstract as much boiler plate code needed to make these web requests as possible  and automatically deserializes the response object  An example of what your code would look like using this wrapper is as simple as     var response   httpClient Get lt SomeResponseObject gt  request            if response StatusCode    HttpStatusCode OK                  do something with the response         console Writeline response Body Id     where the body param matches the object you pass in as an anonymous type         else              do something with the error          console Writelint string Format  quot  0    1  quot   response StatusCode ToString    response ErrorMessage           Full disclosure This library is a free open source wrapper library  and I am the author of said library   I make no money off of this but have found it immensely useful over the years and am sure anyone who is still using the HttpWebRequest   HttpWebResponse classes will too  It is not a silver bullet but supports get  post  delete with both async and non-async for get and post as well as JSON or XML requests and responses   It is being actively maintained as of 6 21 2020

User · Answer

Is this possible using HttpWebRequest and HttpWebResponse    You could have your web server simply catch and write the exception text into the body of the response  then set status code to 500  Now the client would throw an exception when it encounters a 500 error but you could read the response stream and fetch the message of the exception   So you could catch a WebException which is what will be thrown if a non 200 status code is returned from the server and read its body   catch  WebException ex        using  var stream   ex Response GetResponseStream        using  var reader   new StreamReader stream                 Console WriteLine reader ReadToEnd             catch  Exception ex           Something more serious happened        like for example you don t have network access        we cannot talk about a server exception here as        the server probably was never reached

User · Answer

HttpWebRequest myHttprequest   null  HttpWebResponse myHttpresponse   null  myHttpRequest    HttpWebRequest WebRequest Create URL   myHttpRequest Method    POST   myHttpRequest ContentType    application x-www-form-urlencoded   myHttpRequest ContentLength   urinfo Length  StreamWriter writer   new StreamWriter myHttprequest GetRequestStream     writer Write urinfo   writer Close    myHttpresponse    HttpWebResponse myHttpRequest GetResponse    if  myHttpresponse StatusCode    HttpStatusCode OK          Perform necessary action based on response    myHttpresponse Close

[c#] How to get error information when HttpWebRequest.GetResponse() fails

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