Else Use List. You emanet't really argue "oh but I KNOW that I will always pass in a List here", then you should take a List not an IList, else you are breaking Liskov substitution principle: "if S is a subtype of T, then objects of type T may be https://cobjectkullanm30617.blgwiki.com/787361/en_c_ilist_nedir_sırları