Entity Framework Core many to many design problem

user_13287302 0
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the idea is that some kind of entity may have many images and images may be linked to many entities. In addition each many-to-many relationship has a number for an ordering position. So here is what my code looks like:

public abstract class X {
    public int Id{get; private set;}
    public ICollection<ImageLink> ImageLinks{ get; } = new HashSet<ImageLink>();
    ...
}

public class A : X {
    ...
}

public class B : X {
    ...
}

public class <MANY OTHER CLASSES> : X {
    ...
}


public class ImageLink {
    public int EntityId { get; protected set; }
    public int ImageId { get; protected set; }
    public virtual X Entity { get; protected set; }
    public virtual Image Image { get; protected set; }
    public int Position { get; private set; }
    ....
}

I would like my ef core model to have this kind of inheritance because I don't want to repeat some partial views/controllers code and because it makes sense to me. I know I can't do this because the image link entity will be mapped in a single table but I need a table for each many-to-many relationship.

Any ideas?

entity-framework-core asp.net-core entity-framework
1 Answers

You can configure a different image table per entity if you use owned entities

Now, I couldn't get the navigation property to work from ImageLink to X, but it might be possible to do with generics or something.

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<A>().OwnsMany(a => a.ImageLinks, e =>
    {
        e.ToTable("ImageLinksForA");
        e.WithOwner();
    });

    modelBuilder.Entity<B>().OwnsMany(a => a.ImageLinks, e =>
    {
        // Letting EF pick a table name for me
        e.WithOwner();
    });
    
    // Repeat for each descendent of X
}
user_12511270
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