I found strange thing. For example I have Order and Item entity. Item is reference on Order by id. In EF to save Item, I need firstly load Order, and put it to reference field? Is this only way?
        Order order = data.OrderSet.FirstOrDefault(b => b.OrderID == OrderId);
        Item item = new Item { order = order };
        data.AddToAbzacSet(item);
        data.SaveChanges();