using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var animals = new List<Animal>();

        while (true) // Loop indefinitely

        {

            Console.WriteLine("Enter animals (Type 'exit' for stop):"); // Prompt

            string line = Console.ReadLine(); // Get string from user

            if (line == "exit") // Check string

            {

                break;

            }

            EnterAnimal();

        }   

        void EnterAnimal()

        {

            Console.Write("Enter animal name: "); // Report output

            string animalName = Console.ReadLine();

            Console.Write("Enter animal sound: "); // Report output

            string animalSound = Console.ReadLine();

            animals.Add(new Animal(animalName,animalSound));

            Console.Write("Do you want to add another animal (Y/N)"); 

            string answer = Console.ReadLine();

            if (answer == "Y") // Check string

            {

                EnterAnimal();

            }

            else if (answer == "N")

            {

                SingSounds();

            }

        }

        void SingSounds()

        {

            foreach(var animal in animals)

                    {

                        animal.Sing();

                    }

        }       

    }

​

    public class Animal

    {

        private string _name;

        private string _sound;

        public Animal(string name, string sound)

        {

            _name = name;

            _sound = sound;

        }

        public void Sing()

        {

            var song = $@"Old MACDONALD had a farm

                        E-I-E-I-O

                        And on his farm he had a {_name}

                        E-I-E-I-O

                        With a {_sound} {_sound} here

                        And a {_sound} {_sound} there

                        Here a {_sound}, there a {_sound}

                        Everywhere a {_sound} {_sound}

                        Old MacDonald had a farm

                        E-I-E-I-O";

            Console.WriteLine(song);

            Console.WriteLine();

        }

    }

}