If An airline is "countable", this means that there MUST be a flight attendant present on the plane, whose sole job is to count: If you maksat to build a public API, it's better to use IEnumerable than List, because you better use the most minimalistic interface/class. List lets you https://c-object-kullan-m97394.wikirecognition.com/800312/benim_c_ienumerable_nerelerde_kullanılıyor_başlarken_Çalışmak