Field is required. even after filling the field - Validation - asp.net

Question

I am following this course, and the instructor added code to add records to the DB. The class that's going to be added to the DB looks like this:
public class Gig
{
public int Id { get; set; }
public ApplicationUser Artist { get; set; }
[Required]
public string ArtistId { get; set; }
public DateTime DateTime { get; set; }
[Required]
[StringLength(255)]
public string Venue { get; set; }
public Genre Genre { get; set; }
[Required]
public byte GenreId { get; set; }
}
And there's a view model that's attached to the view, to do the mapping, and it looks like this:
public class GigFormViewModel
{
[Required]
public string Venue { get; set; }
[Required]
[FutureDate]
public string Date { get; set; }
[Required]
[ValidTime]
public string Time { get; set; }
[Required]
public byte Genre { get; set; }
[Required]
public IEnumerable<Genre> Genres { get; set; }
public DateTime GetDateTime() => DateTime.Parse($"{Date} {Time}");
}
I have a create method, that gets form fields, and does the mapping from view model to the model itself, and then tries to add the records to the DB, my create action looks like this:
[Authorize]
[HttpPost]
public ActionResult Create(GigFormViewModel viewModel)
{
viewModel.Genres = _context.Genres.ToList();
if (!ModelState.IsValid)
{
return View(viewModel);
}
var gig = new Gig()
{
GenreId = viewModel.Genre,
ArtistId = User.Identity.GetUserId(),
DateTime = viewModel.GetDateTime(),
Venue = viewModel.Venue
};
_context.Gigs.Add(gig);
_context.SaveChanges();
return RedirectToAction("Index", "Home");
}
On the submit, I get the viewModel's property Genres and populate it with the records from the DB, then I check for ModelState.IsValid. but it's giving me:
Genres Field is required
Although I set it just 2 lines above.
Is there something wrong am doing here? Any guidance is appreciated.
Thanks.

Answer 1

You don't need to add a validation data annotation to Genres property in your view model because it is not a data that is set by users but it is set by you to help your view to get a collection of Genre and populate something like a dropdown list.
Firstly, remove the [Required] attribute that decorates your Genres property in GigFormViewModel.
Secondly, refactor your action method, specially the if bloc like below:
[Authorize]
[HttpPost]
public ActionResult Create(GigFormViewModel viewModel)
{
if (!ModelState.IsValid)
{
// re-populate Genres collection only is tha data is in invalid state.
viewModel.Genres = _context.Genres.ToList();
return View(viewModel);
}
// The remainder code does not change
}