c# collection inheritance

Question

Is there a collection in c# that supports the inheritance like concept that objects can have of appearing to include all the elements from another as well as themselves?

Answer 1

Thats not that tricky

// Adding 
Animals.Add( animal );
if( animal is dog )
    Dogs.Add( animal );

//Removing 
Dogs.Remove( animal );
Animals.Remove( animal );

Answer 2

There is nothing provided by MS that can achieve your functionality, however

You could just keep a set of animal and use linq to filter it on the fly:

var animals = new HashSet<Animal>();
var dogs = animals.OfType<Dog>();

Answer 3

Let dogs and cats inherit from an interface, and create HashSet's of the interface instead of the classes. Or use a base class.

for example:

HashSet<IAnimal>