abstract class A
{
    public abstract string GetName();
}

class B : A
{
    public override string GetName() => nameof(B);
}

class C : B
{
    public new string GetName() => nameof(C);
}

public void Test()
{
    A b = new B();
    A c = new C();
    Console.WriteLine(b.GetName() + c.GetName());
}