C#:在不定义新类的情况下创建抽象类的实例

public abstract class Animal
{
    public abstract void MakeSound();
}

public class Dog : Animal
{
    public override void MakeSound()
    {
        Console.WriteLine("Woof!");
    }
}

public class Cat : Animal
{
    public override void MakeSound()
    {
        Console.WriteLine("Meow!");
    }
}

public static void Main(string[] args)
{
    Animal myAnimal = new Dog();
    myAnimal.MakeSound();

    myAnimal = new Cat();
    myAnimal.MakeSound();

    myAnimal = new Animal() { };
    myAnimal.MakeSound();
}