void combo_Changed(object sender, EventArgs e)
{
if (suppressChange) return;
TreeIter t;
combo.GetActiveIter(out t);
IComponent comp = (IComponent) components.GetValue(t, 1);
//Tell everybody about the new selection. We'll hear about this too.
selectionService.SetSelectedComponents ((comp == null)? null : new IComponent[] { comp });
}