Populating entity properties after seeding entities in EF Core

Question

I have the following class, where NextNode points to another instance of the Node class:

public class Node
{
    public int Id { get; set; }
    public int? NextNodeId { get; set; }
    public Node? NextNode { get; set; }
    ...
}

Since I can't reference a node that doesn't yet exist in the NextNode property, is it possible to seed the database in two steps?

First create, the nodes, and then second, populate the NextNode property?

Answer 1

Since you will generate the Ids you can simply fill in the NextNodeId's without filling NextNode for HasData:

modelBuilder.Entity<Node>()
    .HasData(new List<Node>
    {
        new Node
        {
            Id = 1,
            NextNodeId = 2
        },
        new Node
        {
            Id = 2
        }
    });

If you decide to create custom seeding code with Add(Range) + SaveChanges(Async) then you can just create corresponding hierarchy and add it, EF should be able to handle this:

ctx.Nodes.AddRange(new Node
{
    Id = 1, // skip ids if they are database generated
    NextNode = new Node
    {
        Id = 2 // skip ids if they are database generated
    }
});
ctx.SaveChanges();