C#'s type system is a bit messy over there. Besides Func<T> and Action<T>, there's also Predicate<T> , which works the same as Func<T, bool> except for being an entirely different type that's non-trivial to cast to Func<T, bool>. And the whole lot look a lot like delegates.

If they were all just Func<T> (or aliases for that, or wrappers over that when multicast is really needed), it would be a lot simpler.