Question

It loads category but always with null parent. I want get hierarchy category with given ID.

public static Category GetCategory(System.Guid ID, ActionLinkInfo AInfo)
        {
            Category category = null;

            using (TIKSN.STOZE.Data.StozeContext DContext = new Data.StozeContext())
            {
                var cats = from cat in DContext.Categories where cat.ID == ID select cat;

                foreach (Data.Category Cat in cats)
                {
                    category = new Category(Cat, Cat.Parent == null ? null : GetCategory(Cat.Parent.ID, AInfo), AInfo);
                }
            }

            return category;
        }

Answer 1

Try this:

var cats = from cat in DContext.Categories.Include("Parent") where cat.ID == ID select cat;

Or you can change your model, to include that ParentID as an integer in Category class:

public class Category {

    /* (...) */

    public int ParentID { get; set; }

    [ForeignKey("ParentID")]
    public Category Parent { get; set; }
}

With that you’ll be able to get Cat.ParentID without loading whole Parent object from database.