Entity Framework 6.0, Identity, one-to-many relationship not working in IdentityUser class

I am getting crazy with a problem related to Identity and Entity Framework. I am using a code-first approach.

I have these classes:

public class WebApplicationUser : IdentityUser
{
    public virtual ICollection<Favorite> Favorites { get; set; }
}

public class Favorite
{
    public int Id { get; set; }
    public string? ImageName { get; set; }

    public virtual WebApplicationUser WebApplicationUser { get; set; }
}

public class WebApplicationContext : IdentityDbContext<WebApplicationUser>
{
    public WebApplicationContext(DbContextOptions<WebApplicationContext> options)
        : base(options)
    {
    }

    protected override void OnModelCreating(ModelBuilder builder)
    {
        base.OnModelCreating(builder);
        // Customize the ASP.NET Identity model and override the defaults if needed.
        // For example, you can rename the ASP.NET Identity table names and more.
        // Add your customizations after calling base.OnModelCreating(builder);
    }
}

I want to add the Favorites property as shown in the code above.

When I add a new Favorite using code, it's working fine and it's getting transferred to the database.

I do that by getting the current user object

var user = await _userManager.GetUserAsync(HttpContext.User);
user.Favorites.Add

The problem is that for some reason the existing favorites from the database are not filled into my user.Favorites collection (so they are not read back).

When I add elements to the collection they are written to the db but when I try to read the favorites later in another controller action I always get an empty collection.

Does someone have an idea what's going wrong?

I tried different solutions in other forums but nothing is working

You need to use .Include(xx) to load related data in EF Core, So here you can use:

var result  = await _userManager.Users.Include(x=>x.Favorites).Where(x=>x.Id== HttpContext.User.FindFirstValue(ClaimTypes.NameIdentifier)).FirstOrDefaultAsync();

to load user with user.Favorites collection.