//动物类
public abstract class Animal
    {
        public string str = "Animal";

        public void animal()
        {

        }

        public void dog()
        {

        }

    }

//继承动物的狗
public class Dog : Animal
    {
        public string str = "Dog";

        public void animal()
        {

        }

        public void dog()
        {

        }
    }


//使用协变和逆变
static void Main(string[] args)
        {
            Dog dog = new Dog();
            Animal animal = dog;

            List<Dog> dogs = new List<Dog>();
            dogs.Add(dog);

            //下面进行协变:依然会调用自身的方法。这个协变到底有什么作用？直接new Animal本身，直接用他的不就可以了么？干嘛还要这么麻烦呢？
            IEnumerable<Dog> someDogs = dogs;
            IEnumerable<Animal> someAnimals = someDogs;
            someAnimals.ToList()[0].animal();
            someDogs.ToList()[0].animal();

            //public delegate void Action<in T>(T obj);
            //下面进行逆变,同理，为什么这样的动作不在模型类直接在动物类添加“叫”，非要在这里+个方法，然后让狗调用这么麻烦呢？
            Dog aDog = new Dog();

            Action<Animal> actionAnimal = new Action<Animal>(a => { Console.Write("叫"); Console.Read(); });
            Action<Dog> actionDog = actionAnimal;
            actionDog(aDog); 


            
        }