Question

I have a question, why in this code, One() method is execute from class B and Two() method is executed from class A? I know that is doing casting, but I don’t understand the way is working. By the way, any good link or book with this kind of tricks will be much appreciated.
Than you.

class Program
{
    static void Main(string[] args)
    {
        B b = new B();
        A a = (A)b;

        a.One(); 
        a.Two(); 
    }
}

public class A
{
    public virtual void One()
    {
        Console.WriteLine("A One");
    }
    public void Two()
    {
        Console.WriteLine("A Two");
    }
}

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

Answer 1

It is because Two() is not a virtual method. The only time Two() will be called from class B is if you are specifically looking at an instance of B. Class A doesn’t have a lookup table for a virtual method when calling Two() so nobody knows to look elsewhere for a different method.

You can see more details in my answer to this question.