Question

I have an abstract class and two classes derivated of this principal class:

abstract class MainClass
{
    public void DoSomething() {
        if(isEdit())
            Edit();
        else if(isNew())
            New();
        else if(isDelete())
            Delete();
        else if(isSearch())
            Search();
        else if(isExit())
            Exit();
    }

    public abstract void Edit();
    public abstract void New();
    public abstract void Delete();
    public abstract void Search();
    public abstract void Exit();
}

abstract class FirstClass : MainClass
{
    public abstract void Edit();
    public abstract void New();
    public abstract void Delete();
}


abstract class SecondClass : MainClass
{
    public abstract void Search();
    public abstract void Exit();
}

When you need to extend from FirstClass Edit(), New() and Delete() must be declared, and methods Search() and Exit() can be declared but should not be mandatory. Is there any way to do that?

Answer 1

Implement the optional methods as overrides:

abstract class FirstClass : MainClass
{
    public override void Search(){}
    public override void Exit(){}
}

Since they are implemented in MainClass, you don’t need to implement in any inheriting class, but if you want to, you can override them.

Note that you do not need to redeclare Edit, New and Delete again – they are already inherited by FirstClass and will need to be implemented by any non-abstract inheritor of it.