[Gtk-sharp-list] How to highlight the first

[Julien Sobrier]

Hello,
I'm trying to highlight the first row of a TreeView. I tried several
variations around this ode, but none of them has any effect:

TreeIter treeIter;
this.Model.GetIterFirst(out treeIter);
this.Selection.SelectIter(treeIter);


TreeIter treeIter;
this.Model.GetIterFirst(out treeIter);
this.Model.IterChildren(out treeIter);
TreePath treePath = this.Model.GetPath(treeIter);
this.ActivateRow(treePath, null);

TreeIter treeIter;
this.playlistModel.GetIterFirst(out treeIter);
this.Model.IterChildren(out treeIter);
this.Selection.SelectIter(treeIter);

What is the right way to highlight the first row?

Thank you