Is there any way to pass the lambda expression as a variable or argument?

Question

I need to pass the lambda query as a parameter, the followings code is sample and I am interesting to find an implement for it, there is samples: some thing like this:

Answer 1

Well, a lambda is nothing but a delegate, so you could have a method like this:

public void DoIt(IEnumerable a, Action performThis)
{
  performThis(a);
}

But where's the sense in it? Instead of calling a method that applies your lambda, why not calling it directly as you do in the last lines of your code?