Yeah, I hit the problem that there isn't a null-type equivalent of Select() for Action<T>, nor is there a IEnumerable.ForEach (controversial), so that's a bit of a hack. But I wanted to make it as close to the original example as possible.

> There’s no reason to do ToList there

In this case, I would move it to the very end if we are concerned about the underlying data shifting when the collection is actually enumerated.

Forgetting to materialize LINQ results can cause a lot of trouble, oftentimes in ways that happily evade detection while a debugger is attached.

Yes, ForEach isn't idiomatic but he could use Select instead.