EF loading related data issue

Question

I've two entities:

public class Album
{
    public virtual int Id { get; set; }
    public virtual string Name { get; set; }
    public virtual int GenreId { get; set; }
    public virtual int ArtistId { get; set; }
    public virtual string CoverURL { get; set; }
    public virtual int Cost { get; set; }
    public virtual Artist Artist { get; set; }
    public virtual Genre Genre { get; set; }
}

public class Genre
{
    public int Id { get; set; }       
    public string Name { get; set; }
    public virtual IEnumerable<Album> Albums{get;set;}
    public int AlbumCount { get { return Albums.Count(); } }
    public Genre()
    {
        Albums = new List<Album>();
    }
}

and here is the controller action.

public ActionResult Index()
    {
        var genres = db.Genres.ToList();
        return View(genres);
    }

I've one to many mapping between Genre and Album( A album can have only one genre, but a genre can belong to multiple albums). When i try to fetch Album details(including genre nav. property) it gives me expected data. But when i try to display all genres it always gives me 0 as album count. I suspect a binding issue, but i'm unable to find out where. Would be glad if you can help find out the issue.

Answer 1

You must use ICollection instead of IEnumerable for your navigation properties :

public virtual ICollection<Album> Albums { get; set; }

(See this SO answer for example)

Then you can use the Include method to fetch Albums with Genres :

db.Genres.Include(genre => genre.Albums)

or

db.Genres.Include("Albums")

EDIT : read this SO answer for more informations about collection types. Basically, ICollection inherits from IEnumerable , and allows you to modify your collection ( IEnumerable 's main purpose is iteration).

Answer 2

Have you tried this?

public ActionResult Index()
{
    var genres = db.Genres.Include(x => x.Albums).ToList();
    return View(genres);
}