❔ Is saving data from DB into private fields is a good idea?

  public class LessonAppService :ApplicationService,
    ILessonService //implement the IBookAppService
    {
      
        private List<Lesson> _UserLessons;
}

   public async Task<List<LessonDTO>> GetUserLessons()
           
        {
            var queryable = await _lessonRepository.WithDetailsAsync();
            var lessonsQuery= queryable.Where(x=>x.CreatorId == CurrentUser.Id).OrderBy(x=>x.LessonNumber).Take(20);
            var lessons = await lessonsQuery.ToListAsync();
            _UserLessons = lessons;
            return ObjectMapper.Map<List<Lesson>, List<LessonDTO>>(lessons);
            
        }

        private Lesson _activeLesson;