How do I convert a List to List?

Question

I have an interface defined as:

public interface MyInterface {
     object foo { get; set; };
}

and a class that implements that interface:

Answer 1

But a List is emphatically not a List.

Think:

interface IAnimal { }

class Cat : IAnimal { }
class Dog : IAnimal { }

var list = new List { new Cat(), new Dog() };

Then

var cats = (List)list;

Absurd!

Also,

var cats = list.Cast();

Absurd!

Further

var cats = list.ConvertAll(x => (Cat)x);

Absurd!

Instead, you could say

var cats = list.OfType();