public bool RemoveDownloadInfo(DownloadedChapterInfo downloadedChapterInfo) { if (downloadedChapterInfo == null) throw new ArgumentNullException("downloadedChapterInfo"); if (downloadedChapterInfo.ChapterRecord == null) throw new ArgumentException("Invalid chapter record.", "downloadedChapterInfo"); return _storage.RemoveDownloadInfo(downloadedChapterInfo.ChapterRecord.ChapterId); }