using System;

public class Program

{

    interface IAnimal {

        string WhoAmI { get; }

    }

    // *** this is impmenented somewhere where you do not have access to change code, eg. no source code or changes there are not allowed

    class Animal : IAnimal

    {

        public string WhoAmI { get => "I'm Animal"; }

    }

    class ZooRoster

    {

        public void DoVoice(IAnimal animal) 

        {

            Console.WriteLine($"Voice of {animal.WhoAmI}");

        }

    }

    // ^^^ end of external code

    class Deer : Animal, IAnimal 

    {

        string IAnimal.WhoAmI { get => "F*cking Deer"; }

    }

    public static void Main()

    {

        ZooRoster zoo = new ZooRoster();

        zoo.DoVoice(new Deer());

    }

}