Question

I have the following database design for a menuItem table

Id    PId      MenuLink
---   ---      ---------
1     Null     Home.aspx
2     Null     Admin.aspx
3     Null     Logout.aspx
4      2       Manage Content.aspx
5      2       Manage Users.aspx
6      2       Manage Storage.aspx
7      4       Review Content.aspx
8      4       Add New Content.aspx
9      8       Articles.aspx
10     8       News.aspx

It n level hierarchical menu, Root items have Pid Nil & rest have their parent Ids. Now I have a Business object for this table.

public class myMenuItem
{
    public int Id {get; set;}
    public int PId {get; set;}
    public string MenuLink {get; set;}
}

I want to populate my busienss object in such a way that each MenuItem BO would contain the parent & all its child items (n levels)

Currently I first get the Root item, then populate each level one by one with a separate Business object which I created separately(Duplication). Is there a better way to do this task (as my table is single) ?

public class myMenuItem
{
    public int Id {get; set;}
    public int PId {get; set;}
    public string MenuLink {get; set;}
    public List<level1> Level1Items {get ; set;}   
    public List<level2> Level2Items {get ; set;}
}

//  Duplicate class
 public class level1
    {
        public int Id {get; set;}
        public int PId {get; set;}
        public string MenuLink {get; set;}
        // Manually create another list
    }

Answer 1

“Recursive” is the word you’re looking for here. Instead of making classes for each level, you’d want just the myMenuItem, I assume. I’m also going to assume that there isn’t any significance to level1 and level2, that they’re just named like that for uniqueness.

So, your myMenuItem is fine as-is for the example here, except your two lists (Level1Items and Level2Items) should be replaced by List<MenuItem> ChildItems, for example.

For the sake of readability with SO’s colouring, I’ve decided to rename myMenuItem to MyMenuItem.

You could probably do something like this

List<MyMenuItem> MenuItems = <list of your menu items, to save db calls>

List<MyMenuItem> GetMenu()
{
    return MenuItems.Where(f => f.PId == null).Select(GetItem).ToList();
}

MyMenuItem GetItem(MyMenuItem myMenuItem)
{
    var immidiateChildren = MenuItems.Where(m => m.PId == myMenuItem.Id);
    if (immidiateChildren.Any())
        myMenuItem.ChildItems = immidiateChildren.Select(GetItem).ToList();
    return myMenuItem;
}

You’d probably benefit from expanding upon this to instantiate MyMenuItem along the way instead of doing it before you build the tree structure.