It's Always best to use the lowest base type possible. This gives the implementer of your interface, or consumer of your method, the opportunity to use whatever they like behind the scenes. Found this thread while I was looking for a solution to the exact sorun described in the original https://arthurdsbjr.wikibyby.com/789836/c_ilist_nerelerde_kullanılıyor_için_5_İkinci_trick