Classes with Collections as Properties vs. Classes Inheriting Collections

Question

Recently I used a class that inherits from a collection instead of having the collection instantiated within the class, is this acceptable or does it create unseen problems further down the road? Examples below for the sake of clarity:

public class Cars : List<aCar>

instead of something like:

public class Cars
{
 List<aCar> CarList = new List<aCar>();
}

Any thoughts?

Answer 1

The problem with this is that your Cars class will still have the interface it inherits from List, which may allow operations you don't want.

Answer 2

That depends on the final purpose of your class. If it is only going to work as your own implementation of a collection use inheritance. If not, include a a collection as a property. The second option is more versatile:

• As you can only inherit from one class, you might need to inherit from another class rather than collection
• If you need to see this class as a collection you can include an indexer property.