using System;

public class Program

{

    public static void Main()

    {

        var d = new Derivada();

        Console.WriteLine("QuemSouEu: " + d.QuemSouEu());

        Console.WriteLine("QuemSouEuBase: " + d.QuemSouEuBase());

        Console.WriteLine("QuemSouEuThis: " + d.QuemSouEuThis());

        Console.WriteLine("QuemSouEuParseAbstrata: " + d.QuemSouEuParseAbstrata());

        Console.WriteLine("QuemSouEuParseDerivada: " + d.QuemSouEuParseDerivada());

    }

}

​

​

​

public abstract class ClasseAbstrata

{

    public abstract bool Inserir(int x);

    public abstract bool Editar(int x);

    public abstract bool Excluir(int x);

    public string QuemSouEu()

    {

        return "Abstrata";

    }

}

​

public class Derivada : ClasseAbstrata

{

    public override bool  Inserir(int x) { return false; }

    public override bool Editar(int x) { return false; }

    public override bool Excluir(int x) { return false; }

    public string QuemSouEu()

    {

        return "Derivada";

    }

    public string QuemSouEuBase()

    {

        return base.QuemSouEu();

    }

    public string QuemSouEuThis()

    {

        return this.QuemSouEu();

    }

    public string QuemSouEuParseAbstrata()

    {

        return ((ClasseAbstrata)this).QuemSouEu();

    }

    public string QuemSouEuParseDerivada()

    {

        return ((Derivada)this).QuemSouEu();

    }

}