What makes a name of a method equivalent to an action delegate?

Question

I was just experimenting and ended up with the following snippet:

public static class Flow {
    public static void Sequence(params Action[] steps) {
        foreach (var step in steps)
            step();
    }
}
void Main() {
    Flow.Sequence(() => F1(), () => F2());
    Flow.Sequence(F1, F2); // <-- what makes this equiv to the line above?

}
void F1() { }
void F2() { }

I didn't realize that a method name alone was the same as an Action.

What is making this so?

Answer 1

In C#, delegates are nothing more than method pointers. They can point to existing methods in a class, or independent anonymous delegate objects altogether.

This paragraph from the above link should explain what's happening in your code:

Any method that matches the delegate's signature, which consists of the return type and parameters, can be assigned to the delegate. This makes is possible to programmatically change method calls, and also plug new code into existing classes. As long as you know the delegate's signature, you can assign your own delegated method.

That is, when resolving delegate types, what's considered are their signatures, rather than their names.

In your case, your F1() and F2() methods, taking no parameters and returning nothing, have matching signatures with the parameterless Action delegate:

public delegate void Action();

Therefore, they're implicitly convertible to Action.

If you try to pass a method with a different return type or at least one parameter, you'll get a compile-time error as it won't correspond to Action's signature.