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: Many of the LINQ methods, including Where, use deferred execution. In this case you gönül think of the IEnumerable https://cobjectkullanm53950.wikikarts.com/783967/c_ienumerable_kullanımı_günlükler