C#: returning an inherited class from an instance of its base class (generic list)

Question

This is probably me just remembering things completely backwards, but I'd like to know more about what I'm doing wrong...

I have declared a class to be nothing more than a direct inheritance from a generic list (done to simplify naming), something like this:

public class FooList : List<Foo> {}

now in another method completely separate from this class, I am trying to return an instance of this class, however I want to filter the class based on a criterion, so I'm using a lambda expression:

var list = new FooList(); // imagine this fills it with different items
var filtered = list.FindAll(c => c.Something == "filter criteria");

now according to the FindAll method, this SHOULD return a List[Foo]. However, I want to return this object as a FooList, not a List[Foo]. Do I have to create a new instance of FooList and copy the items from the List[Foo]?

If so, why? why can't I convert a List to a FooList directly, since they are the same object?

If this CAN be done, how do I do it?

many thanks!

Answer 1

Your problem is that you are using the wrong tool for the job. Inheritance is not a mechanism for simplifying naming; inheritance is a mechanism primarily designed for (1) modeling "is a kind of" relationships between classes of business domain objects, and (2) enabling the sharing and specialization of implementation details amongst related types.

If you want to simplify naming then the right tool for the job is to put

using FooList = System.Collections.Generic.List<Foo>;

at the top of every file.