private void RunTest()
{
        TreeNode tnSubRoot = treeView.SelectedNode==null?treeView.Nodes[0]:treeView.SelectedNode;
        expandNode2(true, tnSubRoot);
        foreach (TreeNode tn in tnSubRoot.Nodes)
	    {
	        expandNode2(true, tn);
	    }
}
private void expandNode2(bool bExpand, TreeNode tn)
{
    if (tn == null) return;
    if ((tn.IsExpanded && bExpand) ||
        (!tn.IsExpanded && !bExpand)) return;

    tn.TreeView.BeginUpdate();
    if (bExpand)
        tn.Expand();
    else
        tn.Collapse();

    tn.TreeView.EndUpdate();
    Application.DoEvents();
    foreach (TreeNode tnChildren in tn.Nodes)
    {
        expandNode2(bExpand, tnChildren);
    }
}