Why method does not traverse entire tree

Question

I have a method that looks like:

    public IEnumerable<Node> TraverseTree(Node root)
    {            
        if(root.Children != null)
        {
            foreach(var item in root.Children)
                TraverseTree(item);
        }

        yield return root;
    }

and when I do:

var allItems = TraverseTree(someRootNode).ToList();

I only get the first node. Is it not possible to use recursion when using IEnumerable? It will be nice if I can use IEnumerable so that my linq queries do not fully execute.

Edit

Sorry my Node class looks like:

class Node
{
     public Node Val;
     public List<Node> Children = new List<Node>();
}

Similar: http://stackoverflow.com/questions/11830174/how-to-flatten-tree-via-linq — Jacob G, Apr 26 '13 at 19:55
I found a similar solution at: http://stackoverflow.com/a/1043363/637142 I like aquaraga solution better though ;) — Tono Nam, Apr 26 '13 at 19:56

score 2 · Accepted Answer · answered Apr 26 '13 at 19:46

2

It could be rewritten as:

    public IEnumerable<Node> TraverseTree(Node root)
    {
        if (root.Children != null)
        {
            foreach (var child in root.Children)
            {
                var nodes = TraverseTree(child);
                foreach (var node in nodes)
                {
                    yield return node;
                }
            }
        }

        yield return root;
    }

answered Apr 26 '13 at 19:46

aquaraga

4,138
23
29

Yeah, with the original TraverseTree, it's not assigning the return value. – Jonesopolis Apr 26 '13 at 19:50

Why method does not traverse entire tree

Edit

1 Answers1