public void Close(int classId)
        {
            var origin = repository.Get(classId);

            origin.Status = (int)ClassEnums.STATUS_CLOSED;
            repository.Update(origin);
            // update transcript status
            var transcripts = transcriptRepository.GetTranscriptsOfClass(classId).ToList();

            transcripts.ForEach(t =>
            {
                t.Status = (int)TranscriptEnums.STATUS_RESERVE;
            });
            transcriptRepository.UpdateTranscripts(transcripts);
        }