[Vala] signal pepare

[aconsuegra <aconsuegra estudiantes uci cu>]

The signal prepare in the Gtk.Assistant wait by a Widget, these say
http://valadoc.org/?pkg=gtk+-2.0&element=Gtk.Assistant.prepare

but when I try the next code don't work.

rad_local is a RadioButton and credenciales is a Dialog

...
        [CCode(instance_pos=-1)]
        protected void obtener_credenciales(Widget origen){


if(this.rad_local.get_active())
                        {
                var credenciales=new DialogoCredenciales();
                
                switch (credenciales.run())
                {
                case ResponseType.ACCEPT:
                        stdout.printf("acepto");
                        break;
                case ResponseType.CANCEL:
                        credenciales.destroy();
                        break;
                }
                
                        }

        }

...

but if at method I add other parameter with type int,string,bool or char
work fine.

Example

[CCode(instance_pos=-1)]
protected void obtener_credenciales(Widget origen,int pos)

What is the right way??