问使用C# .NET和youtube数据应用编程接口v3检索我的每个YouTube视频的时长

EN

foreach (var channel in channelsListResponse.Items)
{
    var uploadsListId = channel.ContentDetails.RelatedPlaylists.Uploads;

    Console.WriteLine("Videos in list {0}", uploadsListId);

    var nextPageToken = "";
    while (nextPageToken != null)
    {
        var playlistItemsListRequest = youtubeService.PlaylistItems.List("snippet");
        playlistItemsListRequest.PlaylistId = uploadsListId;
        playlistItemsListRequest.MaxResults = 50;
        playlistItemsListRequest.PageToken = nextPageToken;

        // Retrieve the list of videos uploaded to the authenticated user's channel.
        var playlistItemsListResponse = await playlistItemsListRequest.ExecuteAsync();

        foreach (var playlistItem in playlistItemsListResponse.Items)
        {
            var videoRequest = youtubeService.Videos.List("snippet");
            videoRequest.Id = playlistItem.Snippet.ResourceId.VideoId;
            videoRequest.MaxResults = 1;
            var videoItemRequestResponse = await videoRequest.ExecuteAsync();

            // Get the videoID of the first video in the list
            var video = videoItemRequestResponse.Items[0];
            var duration = video.ContentDetails.Duration;
        }

        nextPageToken = playlistItemsListResponse.NextPageToken;
    }
}

    public async Task<List<Video>> GetVideoListAsync(ChannelListMethod Method, string MethodValue, int? MaxVideos)
    {
        // Define variables needed for this method
        List<string> videoIdList = new List<string>();
        List<Video> videoList = new List<Video>();
        string uploadsListId = null;

        // Make sure values passed into the method are not null or empty.
        if (MaxVideos == null)
        {
            throw new ArgumentNullException(nameof(MaxVideos));
        }

        if (string.IsNullOrEmpty(MethodValue))
        {
            return videoList;
        }

        // Create the service.
        using (YouTubeService youtubeService = new YouTubeService(new BaseClientService.Initializer
        {
            ApiKey = _apiKey,
            ApplicationName = _appName
        }))
        {
            // Step ONE is to get a list of channels for a specified YouTube user or ChannelID.
            // Create the FIRST Request object to get a list of YouTube Channels and get their contentDetails
            // based on either ForUserName or ChannelID.
            ChannelsResource.ListRequest channelsListRequest = youtubeService.Channels.List("contentDetails");
            if (Method == ChannelListMethod.ForUserName)
            {
                // Build the ChannelListRequest using UserName
                channelsListRequest.ForUsername = MethodValue;
            }
            else
            {
                // Build the ChannelListRequest using ChannelID
                channelsListRequest.Id = MethodValue;
            }

            // This is the FIRST Request to the YouTube API.
            // Retrieve the contentDetails part of the channel resource to get a list of channel IDs.
            // We are only interested in the Uploads playlist of the first channel.
            try
            {
                ChannelListResponse channelsListResponse = await channelsListRequest.ExecuteAsync();
                uploadsListId = channelsListResponse.Items[0].ContentDetails.RelatedPlaylists.Uploads;
            }
            catch (Exception ex)
            {
                ErrorException = ex;
                return videoList;
            }

            // Step TWO is to get a list of playlist items from the Uploads playlist.
            // From the API response, use the Uploads playlist ID (uploadsListId) to be used to get list of videos
            // from the videos uploaded to the user's channel.
            string nextPageToken = "";
            while (nextPageToken != null)
            {
                // Create the SECOND Request object for requestring a list of Playlist items
                // from the channel's Uploads playlist.
                // Limit the list to maxVideos items and continue to iterate through the pages.
                PlaylistItemsResource.ListRequest playlistItemsListRequest = youtubeService.PlaylistItems.List("contentDetails");
                playlistItemsListRequest.PlaylistId = uploadsListId;
                playlistItemsListRequest.MaxResults = MaxVideos;
                playlistItemsListRequest.PageToken = nextPageToken;

                // This is the SECOND Request to YouTube and get a Response object containing
                // the playlist items in the channel's Uploads playlist.
                // Then iterate through the Response items to build a string list of the video IDs
                try
                {
                    PlaylistItemListResponse playlistItemsListResponse = await playlistItemsListRequest.ExecuteAsync();
                    foreach (PlaylistItem playlistItem in playlistItemsListResponse.Items)
                    {
                        videoIdList.Add(playlistItem.ContentDetails.VideoId.ToString());
                    }
                }
                catch (Exception ex)
                {
                    ErrorException = ex;
                    return videoList;
                }

                // Now that we have a collection (string array) of video IDs,
                // Step THREE is to retrieve the snippet, contentDetails, and statistics parts of the 
                // list of videos uploaded to the authenticated user's channel.
                try
                {
                    // Create the THIRD Request object for requestring a list of videos and their associated metadata.
                    var VideoListRequest = youtubeService.Videos.List("snippet, contentDetails, statistics");
                    // The next line converts the list of video Ids to a comma seperated string array of the video IDs
                    VideoListRequest.Id = String.Join(",", videoIdList);
                    VideoListRequest.MaxResults = MaxVideos;

                    var VideoListResponse = await VideoListRequest.ExecuteAsync();

                    // This is the THIRD Request to the YouTube API to get a Response object
                    // containing Collect each Video duration and convert to a usable time format.
                    foreach (var video in VideoListResponse.Items)
                    {
                        video.ContentDetails.Duration = HMSToTimeSpan(video.ContentDetails.Duration).ToString();
                        videoList.Add(video);
                    }

                    // request next page
                    nextPageToken = VideoListResponse.NextPageToken;
                }
                catch (Exception ex)
                {
                    ErrorException = ex;
                    return videoList;
                }
            }
            return videoList;
        }
    }