EventHandler

void Main()

{

    CustomWorker worker =new CustomWorker();

    worker.DoWork();

}

// You can define other methods, fields, classes and namespaces here

//public delegate void EventHandler(object? sender, EventArgs e);

public abstract class Worker

{

    public abstract event EventHandler WorkStarted;

    public abstract void DoWork();

}

public class CustomWorker : Worker

{

    public override event EventHandler WorkStarted = DoMyWork.EventMethod;

    public override void DoWork()

    {

        Console.WriteLine("Custom work in progress...");

        WorkStarted?.Invoke(this, EventArgs.Empty);

    }

}

public static class DoMyWork

{

    public static void EventMethod(object sender,EventArgs args)

    {

        if (sender != null)

        {

            Console.WriteLine($"{(sender is CustomWorker).ToString()}");

            Console.WriteLine($"sender is = {sender.GetType().ToString()}");

        }

    }

}