C# как сделать enumiration enu

using System;
using System.Collections.Generic;
using System.Linq;

namespace Answers
{
internal class Program
{
private static void Main()
{
var animals = new List<string> { "Коза", "Корова", "Свинья", "Кролик", "Овца", "Гусь" };
var animalsList = new AnimalsList(animals);

Console.WriteLine("Current: " + animalsList.Current());
Console.WriteLine();

Console.WriteLine("Next: " + animalsList.Next());
Console.WriteLine("Next: " + animalsList.Next());
Console.WriteLine("Next: " + animalsList.Next());
Console.WriteLine("Next: " + animalsList.Next());
Console.WriteLine("Next: " + animalsList.Next());
Console.WriteLine("Next: " + animalsList.Next());

Console.WriteLine();
Console.WriteLine("Current: " + animalsList.Current());
Console.WriteLine();

Console.WriteLine("Prevois: " + animalsList.Prevois());
Console.WriteLine("Prevois: " + animalsList.Prevois());
Console.WriteLine("Prevois: " + animalsList.Prevois());
Console.WriteLine("Prevois: " + animalsList.Prevois());
Console.WriteLine("Prevois: " + animalsList.Prevois());
Console.WriteLine("Prevois: " + animalsList.Prevois());

Console.ReadKey();
}
}

public class AnimalsList
{
public AnimalsList()
{
_index = 0;
}

public AnimalsList(List<string> animals)
{
Animals = animals;
_index = 0;
}

public string Next()
{
if (Animals.Last() != Animals[_index]) ++_index;
return Animals[_index];
}

public string Prevois()
{
if (Animals.First() != Animals[_index]) --_index;
return Animals[_index];
}

public string Current()
{
return Animals[_index];
}

public List<string> Animals { get; set; }
private int _index;
}
}