func1 and func 2 are delegates, a type that represent a calling site (a method somewhere).

It's like pointer of function in C/C++, but delegates in C# posses more informations than that (the instance of the object for non static method, ...)

This feature is used in many scenario: Event manamgement, Linq (to object), ...

If compiler produce a binary and the binary works, that's clearly legal.

But, as you don't put parenthesis on a variable, it's better to use Invoke() to clarify the context.

What do you mean by "legal"?
It's just a very spectacular way of solving this issue, but would never found a way into any prod code,
due it's complexity.

But it works for sure and is correct nontheless. :)

Is it legal?

This conditional operator returns function, so second pair of empty parenthesis needed to call returned function.

I know about conditional operator. I want to know how it works with function and why second pair of empty parenthesis needed.

Can somebody please direct me do documentation describing this feature?

(Y)