using static System.Console;

class A {

    virtual public void metodo1() => WriteLine("A");

    public void metodo2() => WriteLine("A");

}

class B : A {

    override public void metodo1() => WriteLine("B");

    public void metodo2() => WriteLine("B");

}

​

public class HelloWorld {

     public static void Main() {

        A a = new A();

        a.metodo1();

        A b = new B();

        b.metodo1();

        A c = new B();

        c.metodo2();

     }

}