The Vala Tutorial has an example about DBus using anonymous methods.
Bus.own_name (BusType.SESSION, \"org.example.DemoService\", /* name to register */
I think there is not way. You must call another process using "def".
Bus.own_name (BusType.SESSION, "org.example.DemoService", BusNameOwnerFlags.NONE, on_bus_aquired, reg, err); def reg() pass def err() print "error"