How do I define the return type of an interface method to be another interface?

Question

I\'m new to interfaces and abstract classes. I want to create a couple of interfaces to define core methods and variables for the objects for a shopping cart system. Then I want

Answer 1

In your abstract class, you should define that the return type of the CartItems property, is of type List.

But, if you really want that the property is of type List, you can maybe do this:

public interface ICart where TCartItem : ICartItem
{
   List CartItems { get; set; }
}

public interface ICartItem
{
}

public abstract class Cart : ICart
{
     public List { get; set; }
}

public abstract class CartItem : ICartItem
{
}