Note That, if your API is only going to be used in foreach loops, etc, then you might want to consider just exposing IEnumerable instead. 1 @supercat: What could ISortableList offer that's not already in IList? Or, asked differently, why couldn't an IList be sorted in-place without re-adding the items https://judahfqrtm.bloguerosa.com/27533468/benim-c-ilist-neden-kullanmalıyız-başlarken-Çalışmak