Else Use List. You can'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://damieneqaip.educationalimpactblog.com/50352579/en-kuralları-of-c-ilist-neden-kullanmalıyız