Formal:
* Avez-vous été en France ? (This is the most formal and grammatically correct way to ask the question.)
Informal:
* Tu es allé(e) en France ? (This is informal and uses the "tu" form of the verb, which is used when speaking to someone you know well.)
* T'es allé(e) en France ? (This is even more informal and uses a contraction of "tu es")
* Es-tu allé(e) en France ? (This is slightly more formal than "tu es allé(e) en France," but still informal.)
Note:
* The verb "aller" (to go) needs to agree with the subject in the past participle. So, "aller" becomes "allé" for masculine subjects and "allée" for feminine subjects.
* "En France" is the correct preposition to use when talking about going to a country.
It's important to choose the appropriate form depending on your relationship with the person you are speaking to.