It’s a misconception that this requires recursion. It will require a stack or a queue and the easiest way is to implement it using recursion. For sake of completeness I’ll provide a non-recursive answer.
static IEnumerable<Node> Descendants(this Node root)
{
var nodes = new Stack<Node>(new[] {root});
while (nodes.Any())
{
Node node = nodes.Pop();
yield return node;
foreach (var n in node.Children) nodes.Push(n);
}
}
Use this expression for example to use it:
root.Descendants().Where(node => node.Key == SomeSpecialKey)