using System;

public class A {

    public void WriteText(){

        Console.WriteLine(GetText());    

    }

    public virtual string GetText(){

        return "A Class";

    }

}

​

public class B : A {

    public override string GetText() {

        return "B class";

    }

}

​

public class Program

{

    public static void Main()

    {

        B b = new B();

        b.WriteText();

    }

}