Depth-first flattened collection of an object hierarchy using LINQ

Question

I have an object hierarchy (MasterNode -> ChildNodes) where master and child nodes are of the same type, and there are only two levels (top level and children) like this (\'

Answer 1

If you have a class like below

public class Node
{
    public string Name;
    public List Children = new List();
}

your linq would be

 Func, IEnumerable> Flatten = null;
 Flatten = coll => coll.SelectMany(n=>n.Concat(Flatten(n.Children)));

Test Code:

Node[] roots = new Node[]{ new Node(){Name="A"},new Node(){Name="B"},new Node(){Name="C"} };
roots[0].Children.Add(new Node(){Name="D"});
roots[0].Children.Add(new Node(){Name="E"});
roots[0].Children.Add(new Node(){Name="F"});

roots[1].Children.Add(new Node(){Name="G"});

roots[2].Children.Add(new Node(){Name="H"});
roots[2].Children.Add(new Node(){Name="I"});

Func, IEnumerable> Flatten = null;
Flatten = coll => coll.SelectMany(n=>n.Concat(Flatten(n.Children)));

var result = String.Join(",",Flatten(roots).Select(x=>x.Name));

Console.WriteLine(result);