animal.cs

public interface IAnimal {
  void Eat();
  void Drink();
  void Sleep();
}
public class Dog : IAnimal {
  public void Eat () {} 
  public void Drink () {} 
  public void Sleep () {} 
}
public class Cat : IAnimal {
  public void Eat () {} 
  public void Drink () {} 
  public void Sleep () {} 
}