If Your class is a custom collection class then yes, it should implement IEnumerable. In this case a public property for the inner list would be redundant. Imagine a simple class: If you plan to build a public API, it's better to use IEnumerable than List, because you better use https://cobjectkullanm19405.national-wiki.com/777924/en_iyi_tarafı_c_ienumerable_kullanımı