Entity Framework 5 codefirst / Required and optional foreign key relations are null

Question

I'm tring to create a DbContext with my entites on entityframework5 codefirst way. I've brands, categories and products.

But when I try to get a Product it's Brand and Category fields are null. Category is optional but Brand is not. So at least the Brand field has to be setted. I tried the code below. Is there any thing that I miss?

    public DbSet<Brand> Brands { get; set; }
    public DbSet<Product> Products { get; set; }
    public DbSet<Category> Categories { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Brand>()
            .HasMany(b => b.Products)
            .WithRequired(p => p.Brand)
            .HasForeignKey(p => p.BrandId);

        modelBuilder.Entity<Category>()
            .HasMany(c => c.Products)
            .WithOptional(p => p.Category)
            .HasForeignKey(p => p.CategoryId);
    }

And on MVC controller side:

    using (var db = new InonovaContext())
    {
        var product = db.Products.Single(p => p.Id == id);
        model.Description = product.Description;
        model.ImageUrl = product.ImageUrl;
        model.Name = product.Name;
        model.BreadCrumb = product.Brand.Name + " / " + product.Category == null ? "" : (product.Category.Name + " / ") + product.Name; // Here Brand and Category are null
    }

Product class is like below

public class Product
{
    public int Id { get; set; }
    public int BrandId { get; set; }
    public virtual Brand Brand { get; set; }
    public string Name { get; set; }
    public int? CategoryId { get; set; }
    public virtual Category Category { get; set; }
    public string ImageUrl { get; set; }
    public string Description { get; set; }
}

Brand class is like below:

public class Brand
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string ThumbLogoImageUrl { get; set; }
    public string Description { get; set; }
    public ICollection<Product> Products { get; set; }
}

Thanks.

Answer 1

If you haven't declared the Brand and Category as virtual, lazyloading of the Brand and Category properties will not work.

public class Product
{
    public int Id { get; set; }
    public string Name { get; set; }

    public virtual Brand Brand { get; set; }
    public int BrandId { get; set; }

    public virtual Category Category { get; set; }
    public int? CategoryId { get; set; }
}

See this for more information on lazy and eager loading.