I keep wanting to do ForEach() on a collection, and noticed that it was inconsistent whether that extension method was available or not. I always figured that i wasn't importing the right namespace, and blamed ReSharper for not being smart enough to figure out what namespace I was missing. So I finally googled the problem only to find this. Turns out ForEach() isn't on IEnumerable, only on Array and List. Meh. But thanks to Dave, i now have it in my core assembly.