public IEnumerator <ITreeItem> TraverseDepthFirst()
{
yield return(Root);
var stack = new Stack <IEnumerator <ITreeItem> >();
stack.Push(Root.GetEnumerator());
while (stack.Count > 0)
{
IEnumerator <ITreeItem> en = stack.Peek();
if (en.MoveNext())
{
ITreeItem n = en.Current;
yield return(n);
if (n.CanSubdivide)
{
en = n.GetEnumerator();
stack.Push(en);
}
}
else
{
stack.Pop();
}
}
}