Code

public IActionResult CreateVacancy([FromBody] VacancyDTO vacancyDTO)
{
    if (vacancyDTO == null)
        return BadRequest(ModelState);

    var existed = _vacancyRepository.GetVacancyByTitle(vacancyDTO.Title);

    if (existed != null)
    {
        ModelState.AddModelError("Existed", "Vacancy with this title already existed");
        return StatusCode(422, ModelState);
    }

    if (!ModelState.IsValid)
    {
        return BadRequest(ModelState);
    }

    var vacancy = _mapper.Map<Vacancy>(vacancyDTO);

    if (!_vacancyRepository.CreateVacancy(vacancy))
    {
        ModelState.AddModelError("Not Created", "Failed To Create");
        return StatusCode(500, ModelState);
    }

    return Ok("Successfully created");
}

When I try to insert a new vacancy, I got this error:

SqlException: Cannot insert explicit value for identity column in table ‘Employers’ when IDENTITY_INSERT is set to OFF.

Even if I insert in vacancies table that depends on employerId and when I insert a new vacancy, I provide an employerId value that exists.

public bool CreateVacancy(Vacancy vacancy)
{
    _context.Vacancies.Add(vacancy);
    return Save();
}