Recursive Hierarchical Parent child

Question

I have a collection of items coming from a database which has a parentid value or null.

Here is my class design:

public class Item
{
public          


        

Answer 1

Using this Node class you can simply do this:

var flatListOfItems = GetItemsFromDatabase();
var rootNodes =Node.CreateTree(flatListOfItems, i => i.id, i => i.ParentId);

Your items doesn't need the subitems anymore because the Node class has a children and a descendants property. (Also ancestors, siblings, level etc.).

The CreateTree method results in 1 or more rootnodes. If you are sure that there is always 1 rootnode, you can do rootNodes.Single() to get the root.