//Adds  a candidate to databse.
        public IActionResult OnPost()
        {
            if (!ModelState.IsValid)
            {
                return(Page());
            }

            _context.Attach(Candidate).State = EntityState.Modified;

            try
            {
                _context.SaveChanges();
            }
            catch (DbUpdateConcurrencyException)
            {
                if (!CandidateExists(Candidate.Id))
                {
                    return(NotFound());
                }
                else
                {
                    throw;
                }
            }

            return(RedirectToPage("./Index"));
        }