gistfile1.cs

private IEnumerable<TreeNode> getAllFileTreeNode(TreeNodeCollection nodes)
{
   foreach (TreeNode f in nodes)
   {
      if (f.Nodes.Count > 0)
      {
         foreach (TreeNode subNode in getAllFileTreeNode(f.Nodes))
            yield return subNode;
      }
      yield return f;
   }
}
foreach (TreeNode node in getAllFileTreeNode(PMTreeView.Nodes))
   if (node is FileNode)
      OnAfterAddFileNode(new FileNodeArgs(node));