TorrentPackage

public TorrentPackage TorrentPackage { get; }

using (Metadata metadata = new Metadata(Constants.InputTorrent))
{
    var root = metadata.GetRootPackage<TorrentRootPackage>();

    root.TorrentPackage.Comment = "test comment";
    root.TorrentPackage.CreatedBy = "GroupDocs.Metadata";
    root.TorrentPackage.CreationDate = DateTime.Today;

    metadata.Save(Constants.OutputTorrent);
}