@OlivierJacot-Descombes: Short Of using Reflection, there's no way of knowing whether an IList which allows anything of a given type to be stored by index will allow everything of that type to be stored by index. I noticed that if I use IEnumerable, when I debug and inspect "sel", which https://rowanahlnr.ja-blog.com/28070137/5-basit-teknikleri-için-c-ienumerable-nerelerde-kullanılıyor