public IActionResult CreateSubject(int schoolId, [FromBody] SubjectDTO subjectDTO) { if (!ModelState.IsValid) { return(BadRequest(ModelState)); } Subject subject = new Subject() { Name = subjectDTO.Name }; ICollection <Subject> schoolSubjects = _schoolRepository.GetAllSubjects(schoolId); foreach (Subject subj in schoolSubjects) { if (subj.Name == subject.Name) { return(Conflict(subject.Name)); } } _schoolRepository.AddSubject(subject, schoolId); return(CreatedAtRoute("GetSubject", new { schoolId, subjectId = subject.Id }, subject)); }