404 when using C# POST to finalise the oAuth Authorization Code Flow

Hi All

Been bashing my head against this one for a while so finally decided I needed some help. I’m using C# to make the final POST in the Authorization Code Flow and it always fails with a 404. Here’s the code which I call after grabbing the callback, I know that the callback works because if I don’t call the final POST I can grab the “code” value and make the request using Postman successfully.

public void TwitchAuthorizationApi(string code)
            HttpWebRequest myWebRequest = null;
            ASCIIEncoding encoding = new ASCIIEncoding();
            Dictionary<string, string> postDataDictionary = new Dictionary<string, string>();

            postDataDictionary.Add("client_id", twitchClientId);
            postDataDictionary.Add("client_secret", twitchClientSecret);
            postDataDictionary.Add("grant_type", "authorization_code");
            postDataDictionary.Add("redirect_uri", twitchRedirectUri);
            postDataDictionary.Add("state", "123456");
            postDataDictionary.Add("code", code);
            string postData = "";

            foreach(KeyValuePair<string, string> kvp in postDataDictionary)
                postData +=  HttpUtility.UrlEncode(kvp.Key) + "=" + HttpUtility.UrlEncode(kvp.Value) + "&";


            byte[] byte1 = encoding.GetBytes(postData);

            myWebRequest = WebRequest.CreateHttp("https://api.twitch.tv/kraken/oauth2/token");

            myWebRequest.Method = "PUT";
            myWebRequest.ContentType = "application/x-www-form-urlencoded";

            myWebRequest.ContentLength = byte1.Length;

            Stream newStream = myWebRequest.GetRequestStream();
            newStream.Write(byte1, 0, byte1.Length);

//Exception happens here and I catch the 404 elsewhere in code
            WebResponse response = myWebRequest.GetResponse();

            newStream = response.GetResponseStream();

            StreamReader myStreamReader = new StreamReader(newStream);
            var jsonResponse = myStreamReader.ReadToEnd();
            myTwitchUtils.DebugLog(String.Format("Response: {0}", jsonResponse));

Any thoughts on what I’ve missed out? I have a theory that it is something to do with the way I am either encoding or placing the data into the POST body but I can’t work out what the problem is. If I take the debug output of the POST body and paste that into Postman the call also succeeds so it must be some subtlety with .Net that I can’t place my finger on


You’re using put, not post.

As an aside, you should be wrapping the response and stream readers in using blocks, or use try… Catch… Finally and dispose so that your aren’t leaking resources.

Thanks so much, can’t believe that the problem was staring me in the face. Appreciate the aside as well, now it’s working it needs a lot of tidying up especially on the exception handling front :slight_smile:

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