C# polymorphism - upcasting

Question

I would like to ask you for an explanation of this example:

public class A : B
{
    public override void Method()
    {
        Console.WriteLine("A");
    }
}

public class B
{
    public virtual void Method()
    {
        Console.WriteLine("B");
    }
}

Equation:

void Main()
{
    B b = (B)new A();

    b.Method(); // result A
}

Why upcasting did not work in this case?

Casting is a compile time concept; the runtime object is still an instance of `A`. — Johnathan Barclay, Sep 24 '21 at 09:43

score 1 · Accepted Answer · answered Sep 24 '21 at 09:46

1

How microsoft docs say:

If you want your derived class to have a member with the same name as a member in a base class, you can use the new keyword to hide the base class member. The new keyword is put before the return type of a class member that is being replaced. The following code provides an example:

answered Sep 24 '21 at 09:46

Den

650
6
15

1

Probably worth mentioning that method hiding is almost always a bad idea. – Johnathan Barclay Sep 24 '21 at 09:57
https://stackoverflow.com/questions/3838553/overriding-vs-method-hiding – Johnathan Barclay Sep 24 '21 at 09:58

C# polymorphism - upcasting

1 Answers1