无法将视频添加到播放列表

Question

我想使用youtube：s API v2将视频添加到现有播放列表。

我可以添加新的播放列表和视频我可以修改播放列表说明和标题。但是当我尝试使用相同的代码块将视频添加到现有播放列表时，没有任何反应。我没有收到错误消息。

这是我的代码：

public static Feed<Playlist> GetAllPlayLists(Video video)
        {
            var request = DoYouTubeRequest();
            Feed<Playlist> userPlaylists = request.GetPlaylistsFeed(Constants.YouTubeCompany);


            foreach (Playlist p in userPlaylists.Entries)
            {
                if (p.Title == "TEST")
                {
                    AddVideoToPlayList(video, p); // Nothings happens
                    p.Summary = "updated summary " + DateTime.Now; // This works
                    request.Update(p);
               }
            }
            return null;
        }

        private static YouTubeRequest DoYouTubeRequest()
    {
        YouTubeRequestSettings settings = new YouTubeRequestSettings("Test", Constants.YouTubeDeveloperKey, Constants.YoutubeUserName, Constants.YoutubePassword);
        YouTubeRequest request = new YouTubeRequest(settings);
        return request;
    }

        public static void AddVideoToPlayList(Video video, Playlist playlist)
        {

        YouTubeRequest request =  DoYouTubeRequest();

        PlayListMember pm = new PlayListMember();
        pm.VideoId = video.VideoId;

            try
            {
                request.AddToPlaylist(playlist, pm);
            }
            catch (Exception ex)
            {
                throw new Exception("Exception in function AddVideoToPlayList:" + ex.Message);
            }
        }

      public static Playlist CreatePlaylist(string title, string summary, Video v)
    {
        if (string.IsNullOrEmpty(title) && string.IsNullOrEmpty(summary))
        {
            throw new ArgumentNullException("title and/or summary is null or empty");
        }

        var request = DoYouTubeRequest();

        Playlist pl = new Playlist();
        pl.Title = title;
        pl.Summary = summary;

        Playlist createdPlaylist = request.Insert(new Uri("https://gdata.youtube.com/feeds/api/users/default/playlists"), pl);
        AddVideoToPlayList(v, createdPlaylist);
        return null;
    }