Use for feminine countries ( en France ) or masculine countries starting with a vowel ( en Iran ). Use au for masculine countries ( au Canada ). Use à for cities ( à Lyon ).
: Many French verbs require a specific preposition before an infinitive or object. For instance: French Prepositions: Forms and Usage
For a deep dive into these structures, resources like the Busuu Guide to Prepositions or the reference book "French Prepositions: Forms and Usage" by Trudie Maria Booth provide comprehensive lists and contextual examples. Use for feminine countries ( en France )
Demander quelqu'un de faire quelque chose (To ask someone to do something). Essayer de (To try to). French Prepositions: Forms and Usage