public void SetToolbarProvider(IToolbarProvider toolbarProvider)
{
PropertyGridToolbar t = toolbar as PropertyGridToolbar;
if (t == null)
throw new InvalidOperationException ("Custom toolbar provider already set");
Remove (t);
foreach (Widget w in t.Children) {
t.Remove (w);
toolbarProvider.Insert (w, -1);
}
t.Destroy ();
toolbarSeparator.Hide ();
toolbar = toolbarProvider;
UpdateTabs ();
}