How does Entity Framework work with recursive hierarchies? Include() seems not to work with it

Question

I have an Item. Item has a Category.

Category has ID, Name, Parent

Answer 1

And now for a completely different approach to hierarchical data, for example populating a treeview.

First, do a flat query for all data, and then build the object graph in memory:

  var items = this.DbContext.Items.Where(i=> i.EntityStatusId == entityStatusId).Select(a=> new ItemInfo() { 
            Id = a.Id,
            ParentId = a.ParentId,
            Name = a.Name,
            ItemTypeId = a.ItemTypeId
            }).ToList();

Get the root item:

 parent = items.FirstOrDefault(a => a.ItemTypeId == (int)Enums.ItemTypes.Root);

Now build your graph:

 this.GetDecendantsFromList(parent, items);


 private void GetDecendantsFromList(ItemInfo parent, List items)
    {
        parent.Children = items.Where(a => a.ParentId == parent.Id).ToList();
        foreach (var child in parent.Children)
        {
            this.GetDecendantsFromList(child,items);
        }
    }