C#: event polymorphism test. Avoid 'overriding' events of parent class.

EventTest.cs

namespace EventTest
{
    using System;

    class Parent
    {
        public event Action Event;

        public virtual void DoEvent()
        {
            Console.WriteLine("\tParent DoEvent In");
            OnEvent();
            Console.WriteLine("\tParent DoEvent Out");
        }

        protected virtual void OnEvent()
        {
            Console.WriteLine("\t\tParent OnEvent In");

            if (Event == null)
            {
                Console.WriteLine("\t\t\tParent OnEvent: Event is null");
            }
            else
            {
                Event();
            }

            Console.WriteLine("\t\tParent OnEvent Out");
        }
    }

    // Not right approach: event handlers will be invoked twice.
    class Alice : Parent
    {
        public override void DoEvent()
        {
            Console.WriteLine("\tAlice DoEvent In");
            base.DoEvent();
            OnEvent();
            Console.WriteLine("\tAlice DoEvent Out");
        }

        protected override void OnEvent()
        {
            Console.WriteLine("\t\tAlice OnEvent In");
            base.OnEvent();
            Console.WriteLine("\t\tAlice OnEvent Out");
        }
    }

    // Not right approach: event handlers will be invoked twice.
    class Bob : Parent
    {
        // Will hide base.Event from outside.
        public new event Action Event;

        public override void DoEvent()
        {
            Console.WriteLine("\tBob DoEvent In");
            base.DoEvent();
            OnEvent();
            Console.WriteLine("\tBob DoEvent Out");
        }

        protected override void OnEvent()
        {
            Console.WriteLine("\t\tBob OnEvent In");
            base.OnEvent();

            if (Event == null)
            {
                Console.WriteLine("\t\t\tBob OnEvent: Event is null");
            }
            else
            {
                Event();
            }

            Console.WriteLine("\t\tBob OnEvent Out");
        }
    }

    // Right approach to 'override' parent's event.
    class Charlie : Parent
    {
        public Charlie()
        {
            base.Event += BaseEventHandler;
        }

        // Will hide base.Event from outside.
        public new event Action Event;

        public override void DoEvent()
        {
            Console.WriteLine("\tCharlie DoEvent In");
            base.DoEvent();
            OnCharlieEvent();
            Console.WriteLine("\tCharlie DoEvent Out");
        }

        private void BaseEventHandler()
        {
            Console.WriteLine("\t\t\tCharlie Knows Base Event Triggered");
        }

        // Prevent overriding OnEvent in descendant classes.
        protected override sealed void OnEvent()
        {
            base.OnEvent();
        }

        protected virtual void OnCharlieEvent()
        {
            Console.WriteLine("\t\tOnCharlieEvent In");

            if (Event == null)
            {
                Console.WriteLine("\t\t\tOnCharlieEvent: Event is null");
            }
            else
            {
                Event();
            }

            Console.WriteLine("\t\tOnCharlieEvent Out");
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            var p = new Parent();
            var a = new Alice();
            var b = new Bob();
            var c = new Charlie();

            Action peh = () => Console.WriteLine("\t\t\tInvoke Parent Event Handler");
            Action aeh = () => Console.WriteLine("\t\t\tInvoke Alice Event Handler");
            Action beh = () => Console.WriteLine("\t\t\tInvoke Bob Event Handler");
            Action ceh = () => Console.WriteLine("\t\t\tInvoke Charlie Event Handler");

            p.Event += peh;
            Console.WriteLine("Invoking Parent DoEvent");
            p.DoEvent();
            Console.WriteLine("Invoked Parent DoEvent");

            a.Event += aeh;
            Console.WriteLine("Invoking Alice DoEvent");
            a.DoEvent();
            Console.WriteLine("Invoked Alice DoEvent");

            b.Event += beh;
            Console.WriteLine("Invoking Bob DoEvent");
            b.DoEvent();
            Console.WriteLine("Invoked Bob DoEvent");

            c.Event += ceh;
            Console.WriteLine("Invoking Charlie DoEvent");
            c.DoEvent();
            Console.WriteLine("Invoked Charlie DoEvent");
        }
    }
}

Output.txt

Invoking Parent DoEvent
        Parent DoEvent In
                Parent OnEvent In
                        Invoke Parent Event Handler
                Parent OnEvent Out
        Parent DoEvent Out
Invoked Parent DoEvent
Invoking Alice DoEvent
        Alice DoEvent In
        Parent DoEvent In
                Alice OnEvent In
                Parent OnEvent In
                        Invoke Alice Event Handler
                Parent OnEvent Out
                Alice OnEvent Out
        Parent DoEvent Out
                Alice OnEvent In
                Parent OnEvent In
                        Invoke Alice Event Handler
                Parent OnEvent Out
                Alice OnEvent Out
        Alice DoEvent Out
Invoked Alice DoEvent
Invoking Bob DoEvent
        Bob DoEvent In
        Parent DoEvent In
                Bob OnEvent In
                Parent OnEvent In
                        Parent OnEvent: Event is null
                Parent OnEvent Out
                        Invoke Bob Event Handler
                Bob OnEvent Out
        Parent DoEvent Out
                Bob OnEvent In
                Parent OnEvent In
                        Parent OnEvent: Event is null
                Parent OnEvent Out
                        Invoke Bob Event Handler
                Bob OnEvent Out
        Bob DoEvent Out
Invoked Bob DoEvent
Invoking Charlie DoEvent
        Charlie DoEvent In
        Parent DoEvent In
                Parent OnEvent In
                        Charlie Knows Base Event Triggered
                Parent OnEvent Out
        Parent DoEvent Out
                OnCharlieEvent In
                        Invoke Charlie Event Handler
                OnCharlieEvent Out
        Charlie DoEvent Out
Invoked Charlie DoEvent

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