Вызов события в производном классе, которое объявлено в базовом

public abstract class A
{
    public event EventHandler<EventArgs> SomeEvent = delegate { };
    public abstract void Foo();
}

public class B : A
{
    public void Foo()
    {
        SomeEvent( this, new EventArgs() );
    }
}

public abstract class A
{
    public abstract event EventHandler<EventArgs> SomeEvent;
    public abstract void Foo();
}
public class B : A
{
    public override event EventHandler<EventArgs> SomeEvent = delegate { };
    public void Foo()
    {
        SomeEvent( this, new EventArgs() );
    }
}

public abstract class Base
{
    public event EventHandler<EventArgs> ExecuteStart = delegate {};
    public abstract event EventHandler<EventArgs> ExecuteStep;
    public event EventHandler<EventArgs> ExecuteCompleted = delegate {};
    public abstract void Execute();
    public void Start()
    {
        ExecuteStart( this, new EventArgs() );
        Execute();
        ExecuteCompleted( this, new EventArgs() );
    }
}
class Derrived : Base
{
    public override event EventHandler<EventArgs> ExecuteStep = delegate {};
    
    public override void Execute()
    {
        ...
        EventHandler( this, new EventArgs() );
        ...
    }

void Main()
{
    B b = new B();
    b.Test += () => Console.WriteLine("1");
    b.Raise();
}
 
class A
{
    public virtual event Action Test;
    
    public void Raise()
    {
        if (Test != null) Test();
    }
}
 
class B : A
{
    public override event Action Test;
}

public abstract class A
{
    public event EventHandler<EventArgs> SomeEvent = delegate { };
    public abstract void Foo();
 
    protected void RaiseSomeEvent(EventArgs e)
    {
        SomeEvent?.Invoke(this, e);
    }
}

public class B : A
{
    public void Foo()
    {
        RaiseSomeEvent(EventArgs.Empty);
    }
}