为什么IsAssignableFrom和GetInterface会给出不同的结果

public class Animal
{
    public virtual void Sound()
    {
        Console.WriteLine("The animal makes a sound");
    }
}

public class Dog : Animal
{
    public override void Sound()
    {
        Console.WriteLine("The dog barks");
    }
}

public class Cat : Animal
{
    public override void Sound()
    {
        Console.WriteLine("The cat meows");
    }
}

Animal animal = new Dog();
Animal animal2 = new Cat();

Console.WriteLine("Is Dog a Dog? " + animal.GetType().IsAssignableFrom(animal.GetType()));
Console.WriteLine("Is Cat a Dog? " + animal2.GetType().IsAssignableFrom(animal2.GetType()));

Console.WriteLine("Does Dog implement Animal? " + animal.GetType().GetInterface(typeof(Animal).FullName));
Console.WriteLine("Does Cat implement Animal? " + animal2.GetType().GetInterface(typeof(Animal).FullName));

Is Dog a Dog? True
Is Cat a Dog? False
Does Dog implement Animal? True
Does Cat implement Animal? False