C#•6mo ago

One-to-many relationships - EF

Hi guys might be a silly question but im confused, if i had a relationship like this

// Principal (parent)
public class Blog
{
    public int Id { get; set; }
    public ICollection<Post> Posts { get; } = new List<Post>(); // Collection navigation containing dependents
}

// Dependent (child)
public class Post
{
    public int Id { get; set; }
    public int BlogId { get; set; } // Required foreign key property
    public Blog Blog { get; set; } = null!; // Required reference navigation to principal
}

// Principal (parent)
public class Blog
{
    public int Id { get; set; }
    public ICollection<Post> Posts { get; } = new List<Post>(); // Collection navigation containing dependents
}

// Dependent (child)
public class Post
{
    public int Id { get; set; }
    public int BlogId { get; set; } // Required foreign key property
    public Blog Blog { get; set; } = null!; // Required reference navigation to principal
}

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<Blog>()
        .HasMany(e => e.Posts)
        .WithOne(e => e.Blog)
        .HasForeignKey(e => e.BlogId)
        .IsRequired();
}

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<Blog>()
        .HasMany(e => e.Posts)
        .WithOne(e => e.Blog)
        .HasForeignKey(e => e.BlogId)
        .IsRequired();
}

when i query posts i still get the data blog without using include. should i confiure the default behavior to no tracking?

8 Replies

Salman•6mo ago

normally in order to fetch the navigation property as well you would need to use the include :

c#
var postsIncludingBlog = _context.Posts.Include(p => p.Blog);

c#
var postsIncludingBlog = _context.Posts.Include(p => p.Blog);

AnoosOP•6mo ago

so if i do something like this var postsIncludingBlog = _context.Posts.ToList(); blog will be null?

Salman•6mo ago

yes

AnoosOP•6mo ago

when im testing it in my code im getting the values without using include

Salman•6mo ago

strange..are you passing the blog explicitly while creating the Post ?

AnoosOP•6mo ago

no i was just querying the table directly I overlooked this part and i think this is whats happening correct me if im wrong. in the same code block i just noticed it was first querying blogs table then later it queries posts so it wasn't null because blogs data is available in the context?

Joschi•6mo ago

If the data is being tracked by the change tracker of your current context instance it will be filled from there. So if you test data fetching or even any kind of manipulation with an DBContext, you should either call context.ChangeTracker.Clear() or create a new context between operations.

AnoosOP•6mo ago

understood thank you guys! :meowheart:

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One-to-many relationships - EF