public void DeleteMentor(Mentor mentor, int schoolId)
{
// firstly, delete mentor in catalogues
List <Domain.Catalogue> catalogues = _context.Catalogues
.Include(c => c.MentorCatalogues).Where(c => c.SchoolId == schoolId).ToList();
List <Domain.MentorCatalogue> deleteMentorCatalogues = catalogues
.SelectMany(c => c.MentorCatalogues).Where(mc => mc.MentorId == mentor.Id).ToList();
_context.RemoveRange(deleteMentorCatalogues);
_context.SaveChanges();
// secondly, delete mentor in school
Domain.Mentor deleteMentor = _context.Mentors.FirstOrDefault(m => m.Id == mentor.Id);
_context.Mentors.Remove(deleteMentor);
_context.SaveChanges();
}
