The class for gtk2, declaring an OnRender method, no linking to gtk3 required:

```c#
class GtkCellRenderer: Gtk.CellRenderer
{
    protected override void Render (Gdk.Drawable window, Gtk.Widget widget, Gdk.Rectangle background_area, Gdk.Rectangle cell_area, Gdk.Rectangle expose_area, Gtk.CellRendererState flags)
    {
        using (var cr = Gdk.CairoHelper.Create (window))
            OnRender (cr, widget, background_area, cell_area, expose_area, flags);
    }

    protected virtual void OnRender (Cairo.Context cr, Gtk.Widget widget, Gdk.Rectangle background_area, Gdk.Rectangle cell_area, CellRendererState flags)
    {
    }
}
```