New input system event

I’ve been trying to understand how to better implement user input, I’ve been watching a particular tutorial:

But whenever I try and make an event such as

public event Action AttackEvent;

I get an error saying:

The type or namespace name 'Actions' could not be found

I swear everything else should be set up correctly, it was only the events that didn’t work. I’ve looked online for similar issues and I haven’t found anything.
Please help.

Action is a delegate that is part of System namespace. So either use:

public event System.Action AttackEvent;

or add this using System; line at the top of the .cs file

using System;