using System;

public class Program

{

    public static void Main()

    {

            // Works as Expected

            var trainer = new Trainer(new Dog());

            Console.WriteLine(trainer.Train());

​

            // Works as Expected

            var dogTrainer = new DogTrainer(new Dog());

            Console.WriteLine(dogTrainer.Train());

​

            // Does not work as expected

            // Calls the Trainer Train not the Dog Trainer Train

            var getTrainer = new Func<Trainer>(() => new DogTrainer(new Dog()));

            var funcTrainer = getTrainer();

            Console.WriteLine(funcTrainer.Train());

​

            // Works as expected 

            var getITrainer = new Func<ITrainer>(() => new DogTrainer(new Dog()));

            var funcITrainer = getITrainer();

            Console.WriteLine(funcITrainer.Train());

​

            // Does not work as expected 

            // Calls the Trainer Train not the Dog Trainer Train

            var getTrainerWithNoInterface = new Func<Trainer>(() => new DogTrainerWithNoInterface(new Dog()));

            var funcTrainerWithNoInterface = getTrainerWithNoInterface();

            Console.WriteLine(funcTrainerWithNoInterface.Train());

​

            // Does not work as expected 

            // Calls the Trainer Train not the Dog Trainer Train

            var getITrainerWithNoInterface = new Func<ITrainer>(() => new DogTrainerWithNoInterface(new Dog()));

            var funcITrainerWithNoInterface = getITrainerWithNoInterface();

            Console.WriteLine(funcITrainerWithNoInterface.Train());

    }

    public class DogTrainer : Trainer, ITrainer

    {

        public DogTrainer(IAnimal animal)

            : base(animal)

        { }

​

        public new string Train()

        {

            return $"Speak Ubu, Speak : {Animal.Speak()}";

        }

    }

​

    public class DogTrainerWithNoInterface : Trainer

    {

        public DogTrainerWithNoInterface(IAnimal animal)

            : base(animal)

        { }

​

        public new string Train()

        {

            return $"Speak Ubu, Speak : {Animal.Speak()}";

        }

    }

​

    public class Trainer : ITrainer

    {

        internal readonly IAnimal Animal;

​

        public Trainer(IAnimal animal)

        {

            Animal = animal;

        }

​

        public string Train()

        {

            return Animal.Speak();

        }

    }

​

    public interface ITrainer

    {

        string Train();

    }

​

    public class Dog : IAnimal

    {

        public string Speak()

        {

            return "Woof";

        }

    }

​

    public interface IAnimal

    {

        string Speak();

    }   

}