> No return value needed (compiles down to an Action<T> I think)

Which is an other crufty thing in C#: because Void/() is not a type (inherited from Java), it needs to have both `Func<Tn..., T>` and `Action<Tn...>` in order to handle functions-with-a-return-value and functions-without-a-return-value.

This is true, but its mostly transparent unless you're doing something particularly ugly.

Like trying to take one of these as parameter or return it?

This is a statically typed language mind you. If you're passing something around as values, you're gonna need to declare what its type is (of course there's type inference, but that just turns it into a totally different language)

> If you're passing something around as values, you're gonna need to declare what its type is

I fail to see the relation this has with my issue.

You should need to know whether you require the lambda you're accepting to return some value or not, and its type.

You completely missed the point I was making. Try reading these comments again.

Can't recursively call a lambda function, no thanks.

There are two ways of recursively calling lambda functions, neither perfect, but both usable.

  Func<int,int> fib = null;
  fib = n => n > 1 ? fib(n - 1) + fib(n - 2) : n;

Or write yourself a Y fixed-point combinator, described in http://blogs.msdn.com/b/wesdyer/archive/2007/02/02/anonymous...

  delegate Func<A,R> Recursive<A,R>(Recursive<A,R> r);
  static Func<A, R> Y<A, R>(Func<Func<A, R>, Func<A, R>> f) {
    Recursive<A, R> rec = r => a => f(r(r))(a);
    return rec(rec);
  }

used like this:

  Func<int,int> fib = Y<int,int>(f => n => n > 1 ? f(n - 1) + f(n - 2) : n);

(I'm not advocating writing a fib function this way, but it's a useful example!)