Violation of OO concepts?

Question

Create a base class with a method that uses a switch case that reference the type of the children class.

Is the below piece of code violating the OO principles, if so which one?

public abstract class BaseClass
{
    public BaseClass Method()
    {
        switch (this)
        {
            case DerivedClass1 s:
                return new DerivedClass1();
            case DerivedClass2 c:
                return new DerivedClass2();
            case DerivedClass3 r:
                return new DerivedClass3();
            default:
                return null;
        }
    }
}

[Liskov substitution principle](https://en.wikipedia.org/wiki/Liskov_substitution_principle) — Cid, Aug 18 '20 at 12:52
https://meta.stackoverflow.com/questions/334822/how-do-i-ask-and-answer-homework-questions — Num Lock, Aug 18 '20 at 12:53

score 4 · Accepted Answer · answered Aug 18 '20 at 12:53

You're violating the open-closed principle of SOLID by not taking advantage of polymorphism. Make the base class method virtual and override it for each derived class:

public abstract class BaseClass
{
    public virtual BaseClass Method()
    {
        return null;
    }
}

public class DerivedClass1 : BaseClass
{
    public override BaseClass Method()
    {
        return new DerivedClass1();
    }
}

...and so on.

Violation of OO concepts?

1 Answers1