How would you handle DLC with the steamworks extension?

On the steamworks documentation it says:
"Steamworks games can check if a user owns and has downloaded a piece of downloadable content using SteamApps()->BIsDlcInstalled(DLCAppID)."

Does "Owns another AppID" in the Steamworks extension work the same way? In which case, how would you get it to work in offline mode as well - I've tried using the event before but it only works online.