nContextMenu1.PaletteInheritance = PaletteInheritance.None;
nContextMenu1.Palette.HighlightLight = color1;
nContextMenu1.Palette.HighlightDark = color2;

treeView.Scrollable = false;

treeView.NodeMouseClick += TreeView_NodeMouseClick;

private void TreeView_NodeMouseClick(object sender, TreeNodeMouseClickEventArgs e)
{
    NTreeView view = sender as NTreeView;

    int lastIndex = view.Nodes.Count - 1;
    TreeNode lastNode1stLevel = view.Nodes[lastIndex];
    TreeNode lastNode = GetNextVisibleNodeRecursive(lastNode1stLevel);
    view.Height = lastNode.Bounds.Bottom;
}

private TreeNode GetNextVisibleNodeRecursive(TreeNode node)
{
    TreeNode nextNode = node.NextVisibleNode;
    if (nextNode == null)
    {
        return node;
    }
    else
    {
        nextNode = GetNextVisibleNodeRecursive(nextNode);
    }

    return nextNode;
}