Rendering a hierarchy using LINQ?

Question

Let say we have a class

Category
{
   ID,
   Name,
   ParentID
}

and a List

1, \'Item 1\', 0
2, \'Item 2\', 0
3, \'Item 3\'         


        

Answer 1

 public IEnumerable GetHelpPageMenuItems()
    {
        var helpPages = (from h in Context.HelpPages select new HelpPageMenuItem{HelpPageId = h.HelpPageId, ParentHelpPageId = h.ParentHelpPageId, PageContext = h.PageContext, MenuText = h.MenuText}).ToList();
        var parents = from h in helpPages where !h.ParentHelpPageId.HasValue select PopulateChildren(h, helpPages);
        return parents.ToList();
    }

    private static HelpPageMenuItem PopulateChildren(HelpPageMenuItem helpPageMenuItem, IEnumerable helpPages)
    {
        helpPageMenuItem.ChildHelpPages =
            (from h in helpPages
             where h.ParentHelpPageId == helpPageMenuItem.HelpPageId
             select PopulateChildren(h, helpPages)).ToList();

        return helpPageMenuItem;
    }