How to flatten tree via LINQ?

Question

So I have simple tree:

class MyNode
{
 public MyNode Parent;
 public IEnumerable Elements;
 int group = 1;
}

I have a I

Answer 1

Here some ready to use implementation using Queue and returning the Flatten tree me first and then my children.

public static IEnumerable Flatten(this IEnumerable items, 
    Func> getChildren)
    {
        if (items == null)
            yield break;

        var queue = new Queue();

        foreach (var item in items) {
            if (item == null)
                continue;

            queue.Enqueue(item);

            while (queue.Count > 0) {
                var current = queue.Dequeue();
                yield return current;

                if (current == null)
                    continue;

                var children = getChildren(current);
                if (children == null)
                    continue;

                foreach (var child in children)
                    queue.Enqueue(child);
            }
        }

    }