Animal

namespace TemplateMethod
{
    public interface Animal
    {
        string GetVoice();
    }

    public class Dog : Animal
    {
        public string GetVoice()
        {
            return "わん";
        }
    }

    public class Cat : Animal
    {
        public string GetVoice()
        {
            return "にゃー";
        }
    }
}

Program

using System;
using System.Collections.Generic;

namespace TemplateMethod
{
    internal class Program
    {
        private static void Main(string[] args)
        {
            //ポリモーフィズムのテストコード

            var animalList = new List<Animal>
            {
                new Dog(),
                new Cat(),
            };

            foreach (var animal in animalList)
            {
                Console.WriteLine(animal.GetVoice());
            }
        }
    }
}