Problems with C# HTTP Post with Authentication

Question

I'm trying to send some XML through HTTP Post. But I'm getting 401 Unauthorized. Funny thing is when I access the URL through the browser, the username/password I provide are OK.

Here is my method signature:

        internal static string Send(string URL, string XMLdata, string RequestMethod, 
                                    string RequestUsername, string RequestPassword)

I have tried this as method body:

        string requestData = XMLdata;
        string responseData = "";

        StreamWriter myWriter = null;
        HttpWebRequest objRequest = (HttpWebRequest)WebRequest.Create(URL);

        objRequest.Method = RequestMethod;
        objRequest.PreAuthenticate = true;
        objRequest.ContentType = "application/x-www-form-urlencoded";//"text/xml";
        objRequest.Credentials = new NetworkCredential(RequestUsername, RequestPassword);;
        objRequest.ContentLength = requestData.Length;

        try
        {
            myWriter = new StreamWriter(objRequest.GetRequestStream());
            myWriter.Write(requestData);
        }
        finally
        {
            myWriter.Close();
        }

        StreamReader sr = null;

        try
        {
            HttpWebResponse objResponse = (HttpWebResponse)objRequest.GetResponse();
            sr = new StreamReader(objResponse.GetResponseStream());
            responseData = sr.ReadToEnd();
        }
        finally
        {
            if (sr != null)
                sr.Close();
        }

        return responseData;

And also this:

        string result;

        using (var client = new WebClient())
        {
            Uri requestUri = new Uri(URL);
            CredentialCache cache = new CredentialCache();
            NetworkCredential nc = new NetworkCredential(RequestUsername, RequestPassword);
            cache.Add(requestUri, "Basic", nc);
            client.Credentials = cache;

            result = client.UploadString(requestUri, XMLdata);
        }

        return result;

Both get the 401. What am I doing wrong? Just a reminder: when I access the URL through the browser, it prompts for username/password and the credentials I provide are OK.

My readings on the subject so far:

I appreciate the help.

I don't have an answer for you, from your description, but I do have a suggestion: use Fiddler to see what the request and response look like, both when the browser request succeeds, and when the programmatic request fails. I suspect there will be a difference that jumps out at you. — jwismar
"it prompts for username/password" - in a popup window? Then it is Win auth. — Tomas Voracek
Yes, it prompts in a browser popup window, no matter what browser. Are you sure that makes this a Windows Authentication? Either way, do you know what I change in the codes I posted? — Adriano Carneiro
@jwismar Great tip, will do and let you know the outcome. BTW, you should post that as an answer — Adriano Carneiro

jwismar jwismar · Accepted Answer · 2011-05-24T21:55:34

[At request of OP, I'm migrating my comment to an answer]

I don't have an answer for you, from your description, but I do have a suggestion: use Fiddler to see what the request and response look like, both when the browser request succeeds, and when the programmatic request fails. I suspect there will be a difference that jumps out at you.

Problems with C# HTTP Post with Authentication

2 Answers