Youtube API v3 with OAuth2 return "Received verification code. Closing..."

Question

I'm trying to upload a video in youtube with C# Win application with the code below:

    public Form1()
    {
        InitializeComponent();

        Console.WriteLine("YouTube Data API: Upload Video");
        Console.WriteLine("==============================");

        try
        {
            new UploadVideo().Run().Wait();
        }
        catch (AggregateException ex)
        {
            foreach (var e in ex.InnerExceptions)
            {
                //Console.WriteLine("Error: " + e.Message);
            }
        }

        Console.WriteLine("Press any key to continue...");
        Console.ReadKey();
    }

This is the class UploadVideo:

internal class UploadVideo
{
    public async Task Run()
    {
        UserCredential credential;
        using (var stream = new FileStream(@"C:\Users\23679\Downloads\client_secret.json", FileMode.Open, FileAccess.Read))
        {
            credential = await GoogleWebAuthorizationBroker.AuthorizeAsync(
                GoogleClientSecrets.Load(stream).Secrets,
                new[] { YouTubeService.Scope.YoutubeUpload },
                "user",
                CancellationToken.None
            );
        }

        var youtubeService = new YouTubeService(new BaseClientService.Initializer()
        {
            HttpClientInitializer = credential,
            ApplicationName = Assembly.GetExecutingAssembly().GetName().Name
        });

        var video = new Video();
        video.Snippet = new VideoSnippet();
        video.Snippet.Title = "Default Video Title";
        video.Snippet.Description = "Default Video Description";
        video.Snippet.Tags = new string[] { "tag1", "tag2" };
        video.Snippet.CategoryId = "22";
        video.Status = new VideoStatus();
        video.Status.PrivacyStatus = "private";
        var filePath = @"C:\Users\23679\Downloads\spacetestSMALL.wmv";

        using (var fileStream = new FileStream(filePath, FileMode.Open))
        {
            var videosInsertRequest = youtubeService.Videos.Insert(video, "snippet,status", fileStream, "video/*");
            videosInsertRequest.ProgressChanged += videosInsertRequest_ProgressChanged;
            videosInsertRequest.ResponseReceived += videosInsertRequest_ResponseReceived;

            await videosInsertRequest.UploadAsync();
        }

    }

    void videosInsertRequest_ProgressChanged(Google.Apis.Upload.IUploadProgress progress)
    {
        switch (progress.Status)
        {
            case UploadStatus.Uploading:
                Console.WriteLine("{0} bytes sent.", progress.BytesSent);
                break;

            case UploadStatus.Failed:
                Console.WriteLine("An error prevented the upload from completing.\n{0}", progress.Exception);
                break;
        }
    }

    void videosInsertRequest_ResponseReceived(Video video)
    {
        Console.WriteLine("Video id '{0}' was successfully uploaded.", video.Id);
    }

It runs ok, then a browser window open asking permition like below:

The problem is that he return this message in the browser after i confirm:

So, I have two questions. What this message means?

And the second is, After that, what should happened? Because, the video is not uploaded and the debug don't continue...

Answer 1

I am not familiar with C# but I have some basic knowledge of OAuth 2.0 Authorization Code grant. I have made a web-sequence diagram which can help you.

On the first screenshot you shared the URI contains a redirect_uri query parameter with your callback url. This request gets a response with HTTP 302 redirect to the callback uri with the code=... query parameter. You application should handle this request and exchange this code to an access_token.

My assumption that you can find C# libraries which helps you to handle these redirections and callas in order to receive an access_token and also a refresh_token, like in the RFC:

Response from OAuth 2.0 compliant server:

HTTP/1.1 302 Found
Location: https://client.example.com/cb?code=SplxlOBeZQQ&state=xyz

Local application should forge this request:

 POST /token HTTP/1.1
 Host: server.example.com
 Authorization: Basic czZCaGRSa3F0MzpnWDFmQmF0M2JW
 Content-Type: application/x-www-form-urlencoded     
 
 grant_type=authorization_code&code=SplxlOBeZQQ
 &redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb

Response from the OAuth 2.0 compliant server:

 HTTP/1.1 200 OK
 Content-Type: application/json;charset=UTF-8
 Cache-Control: no-store
 Pragma: no-cache

 {
   "access_token":"2YotnFZFEjr1zCsicMWpAA",
   "token_type":"example",
   "expires_in":3600,
   "refresh_token":"tGzv3JOkF0XG5Qx2TlKWIA",
   "example_parameter":"example_value"
 }

This websequence diagram I made could be a good explanation.