box api - Box API always returns invalid grant_type parameter on obtaining access token

Question

I'm writing my own Box SDK for WP8 to make the most out of Tasks. I am having trouble obtaining an access token. I always get this as a return:

{"error":"invalid_request","error_description":"Invalid grant_type parameter or parameter missing"}

The code (all in C#) I'm using is:

    internal const String TokenURL = "https://api.box.com/oauth2/token";

CloudHttpAsync.DownloadResponceStreamAsync
(
    CloudHttpAsync.PostAsync
    (
        TokenURL,
        new MemoryStream
        (
            UTF8Encoding.UTF8.GetBytes
            (
                HttpUtility.UrlEncode
                (
                    String.Format
                    (
                        "grant_type=authorization_code&code={0}&client_id={1}&client_secret={2}&redirect_uri={3}",
                        Code,
                        ClientID,
                        ClientSecret,
                        RedirectURI
                    )
                )
            )
        ),
        null,
        null
    ),
    null
).ContinueWith((AsyncStream) =>
    {
        try
        {
            if (AsyncStream.Exception != null)
            {
                TaskSource.TrySetException(AsyncStream.Exception.InnerExceptions);
                return;
            }

            String Result = "";
            using (StreamReader Reader = new StreamReader(AsyncStream.Result))
            {
                Result = Reader.ReadToEnd();
            }

            BoxAuthToken Token = JsonConvert.DeserializeObject<BoxAuthToken>(Result);
            TaskSource.TrySetResult(Token);
        }
        catch (Exception e)
        {
            TaskSource.TrySetException(e);
        }
    });

and

    public static Task<HttpWebResponse> PostAsync(String URL, Stream UploadData, IRequestSigner Signer, IProgress<NetworkProgress> Progress)
    {
        TaskCompletionSource<HttpWebResponse> TaskSource = new TaskCompletionSource<HttpWebResponse>();

        HttpWebRequest Request = WebRequest.CreateHttp(URL);
        Request.Method = "POST";

        if (Signer != null)
        {
            Signer.Sign(Request).ContinueWith((o) =>
            {
                if (o.Exception != null)
                {
                    TaskSource.TrySetException(o.Exception.InnerExceptions);
                    return;
                }

                UploadDataAsync(Request, UploadData, Progress).ContinueWith((AsyncRequest) =>
                {
                    if (AsyncRequest.Exception != null)
                    {
                        TaskSource.TrySetException(AsyncRequest.Exception.InnerExceptions);
                        return;
                    }

                    GetResponceAsync(Request).ContinueWith((AsyncResponce) =>
                    {
                        if (AsyncResponce.Exception != null)
                        {
                            TaskSource.TrySetException(AsyncResponce.Exception.InnerExceptions);
                            return;
                        }

                        TaskSource.TrySetResult(AsyncResponce.Result);
                    });
                });
            });
        }
        else
        {
            UploadDataAsync(Request, UploadData, Progress).ContinueWith((AsyncRequest) =>
            {
                if (AsyncRequest.Exception != null)
                {
                    TaskSource.TrySetException(AsyncRequest.Exception.InnerExceptions);
                    return;
                }

                GetResponceAsync(Request).ContinueWith((AsyncResponce) =>
                {
                    if (AsyncResponce.Exception != null)
                    {
                        TaskSource.TrySetException(AsyncResponce.Exception.InnerExceptions);
                        return;
                    }

                    TaskSource.TrySetResult(AsyncResponce.Result);
                });
            });
        }

        return TaskSource.Task;
    }

    internal static Task<HttpWebRequest> UploadDataAsync(HttpWebRequest Request, Stream Data, IProgress<NetworkProgress> Progress)
    {
        TaskCompletionSource<HttpWebRequest> TaskSource = new TaskCompletionSource<HttpWebRequest>();

        if (Data.Length != 0)
        {
            Request.ContentLength = Data.Length;
            Request.AllowWriteStreamBuffering = false;

            Request.BeginGetRequestStream(new AsyncCallback((IAR) =>
                {
                    try
                    {
                        using (Stream UploadStream = Request.EndGetRequestStream(IAR))
                        {
                            Int64 Upload = 0;
                            Int64 TotalUploaded = 0;
                            Int64 Total = Data.Length;
                            Byte[] Buffer = new Byte[4096];

                            while (TotalUploaded < Total)
                            {
                                Upload = Data.Read(Buffer, 0, Buffer.Length);
                                TotalUploaded += Upload;
                                UploadStream.Write(Buffer, 0, (Int32)Upload);

                                if (Progress != null)
                                {
                                    Progress.Report(new NetworkProgress()
                                    {
                                        Operation = NetworkOperation.Uploading,
                                        TotalBytes = Total,
                                        BytesProcessed = TotalUploaded
                                    });
                                }
                            }
                        }

                        TaskSource.TrySetResult(Request);
                    }
                    catch (Exception e)
                    {
                        TaskSource.TrySetException(e);
                    }
                }),
                null);
        }
        else
        {
            TaskSource.TrySetResult(Request);
        }

        return TaskSource.Task;
    }

    internal static Task<HttpWebResponse> GetResponceAsync(HttpWebRequest Request)
    {
        TaskCompletionSource<HttpWebResponse> TaskSource = new TaskCompletionSource<HttpWebResponse>();

        Request.BeginGetResponse(new AsyncCallback((IAR) =>
            {
                try
                {
                    HttpWebResponse Responce = (HttpWebResponse)Request.EndGetResponse(IAR);
                    TaskSource.TrySetResult(Responce);
                }
                catch (Exception e)
                {
                    if (e is WebException && (e as WebException).Response.ContentLength > 0)
                    {
                        TaskSource.TrySetResult((HttpWebResponse)(e as WebException).Response);
                    }
                    else
                    {
                        TaskSource.TrySetException(e);
                    }
                }
            }),
            null);

        return TaskSource.Task;
    }

    public static Task<StreamAndLength> GetResponceStreamAsync(Task<HttpWebResponse> Task)
    {
        TaskCompletionSource<StreamAndLength> TaskSource = new TaskCompletionSource<StreamAndLength>();

        Task.ContinueWith((AsyncHWR) =>
            {
                if (AsyncHWR.Exception != null)
                {
                    TaskSource.TrySetException(AsyncHWR.Exception.InnerExceptions);
                    return;
                }

                HttpWebResponse Responce = AsyncHWR.Result;
                TaskSource.TrySetResult( new StreamAndLength() { Stream = Responce.GetResponseStream(), Length = Responce.ContentLength });
            });

        return TaskSource.Task;
    }

    public static Task<MemoryStream> DownloadResponceStreamAsync(Task<HttpWebResponse> Task, IProgress<NetworkProgress> Progress)
    {
        TaskCompletionSource<MemoryStream> TaskSource = new TaskCompletionSource<MemoryStream>();

        GetResponceStreamAsync(Task).ContinueWith((AsyncStream) =>
            {
                if (AsyncStream.Exception != null)
                {
                    TaskSource.TrySetException(AsyncStream.Exception.InnerExceptions);
                    return;
                }

                MemoryStream MemStream = new MemoryStream();
                MemStream.SetLength(AsyncStream.Result.Length);

                Int64 CurrentRead = 0;
                Int64 TotalRead = 0;
                Int64 Total = AsyncStream.Result.Length;
                Byte[] Buffer = new Byte[4096];

                using (Stream DownloadStream = AsyncStream.Result.Stream)
                while (TotalRead < Total)
                {
                    CurrentRead = DownloadStream.Read(Buffer, 0, Buffer.Length);
                    MemStream.Write(Buffer, 0, (Int32)CurrentRead);
                    TotalRead += CurrentRead;

                    if (Progress != null)
                    {
                        Progress.Report(new NetworkProgress()
                        {
                            Operation = NetworkOperation.Downloading,
                            TotalBytes = Total,
                            BytesProcessed = TotalRead
                        });
                    }
                }

                MemStream.Position = 0;
                TaskSource.TrySetResult(MemStream);
            });

        return TaskSource.Task;
    }

    internal class StreamAndLength
    {
        public Stream Stream { get; set; }
        public Int64 Length { get; set; }
    }

Sorry there is a lot of code, I like to write generically :)

Edit: Raw Responces (ClientID & Client Secret removed)

When URL encoding each value:

POST https://api.box.com/oauth2/token HTTP/1.1
Accept: */*
Content-Length: 196
Accept-Encoding: identity
User-Agent: NativeHost
Host: api.box.com
Connection: Keep-Alive
Cache-Control: no-cache

grant_type=authorization_code&code=JknaLbfT6lAXmey3FLYrp9eg1jMbpFuQ&client_id=[subbed]&client_secret=[subbed]&redirect_uri=https%3a%2f%2fCloudBoxWP8

Return:

HTTP/1.1 400 Bad Request
Server: nginx
Date: Fri, 01 Mar 2013 07:35:22 GMT
Content-Type: application/json
Connection: keep-alive
Set-Cookie: box_visitor_id=51305a3a187f34.52738262; expires=Sat, 01-Mar-2014 07:35:22 GMT; path=/; domain=.box.com
Set-Cookie: country_code=US; expires=Tue, 30-Apr-2013 07:35:22 GMT; path=/
Cache-Control: no-store
Content-Length: 99

{"error":"invalid_request","error_description":"Invalid grant_type parameter or parameter missing"}

When URL encode the entire string:

POST https://api.box.com/oauth2/token HTTP/1.1
Accept: */*
Content-Length: 214
Accept-Encoding: identity
User-Agent: NativeHost
Host: api.box.com
Connection: Keep-Alive
Cache-Control: no-cache

grant_type%3dauthorization_code%26code%3d3ikruv5elfdw3fOP55aMDSX7ybLqBFlA%26client_id%3d[subbed]%26client_secret%3d[subbed]%26redirect_uri%3dhttps%3a%2f%2fCloudBoxWP8

Return

HTTP/1.1 400 Bad Request
Server: nginx
Date: Fri, 01 Mar 2013 07:46:03 GMT
Content-Type: application/json
Connection: keep-alive
Set-Cookie: box_visitor_id=51305cbb339de4.03221876; expires=Sat, 01-Mar-2014 07:46:03 GMT; path=/; domain=.box.com
Set-Cookie: country_code=US; expires=Tue, 30-

Answer 1

It's not listed anywhere on the Box API documentation, but the request for retrieving the access token requires the header Content-Type: application/x-www-form-urlencoded

I was also stuck on this part for a while until I found the answer on StackOverflow. I forget the link to it though.