Question

I extra said derived classes and NOT children classes.

I have a base class and many derived classes. One derived class should call a method on the base class which again is calling a method on each derived class.

How is that possible? What design pattern should I go for implemention a communication

“channel” between my Controllers driving the UI using MVVM design pattern? I know of mediator

pattern but do not like it much as it blurs the borders of an architecture.

Answer 1

It’s not really a design pattern, but really an understanding of virtual method calls. Let’s say I have something:

public abstract class Foo
{
    protected void DoFoo()
    {
        DoFooInternal();
    }

    protected abstract void DoFooInternal();
}

And I have a derived class:

public class Bar : Foo
{
    protected override void DoFooInternal()
    {
        // Something here
    }
}

In the above example, any call to DoFoo on the base class makes a virtual call to the DoFooInternal method of the derived class. I could also define my DoFooInternal as virtual, if I wanted to provide a baseline implementation:

protected virtual void DoFooInternal()
{
   // Baseline implementation here
}

In the case of your controllers, this would be the same, you can specify some common shared logic in a ControllerBase instance and derive a child controller, e.g. PeopleController which can despatch method calls to the base class, which can in turn despatch calls back to virtual methods in the derived class…