loading a full hierarchy from a self referencing table with EntityFramework.Core

Question

Explanation why this question is different to: EF - multiple includes to eager load hierarchical data. Bad practice?

1. the possible duplicate is an opinion based

Answer 1

In fact loading the whole hierarchy is quite easy thanks to the so called EF (Core) relationship fixup.

Let say we have the following model:

public class Hierarchy
{
    public int Id { get; set; }
    public string Name { get; set; }
    public Hierarchy Parent { get; set; }
    public ICollection Children { get; set; }
}

Then the following code

var hierarchy = db.Hierarchy.Include(e => e.Children).ToList();

will load the whole hierarchy with correctly populated Parent and Children properties.

The problem described in the referenced posts arise when you need to load just part of the hierarchy, which is hard due to the lack of CTE like support in LINQ.