Generic Collections - Ensuring Collections Contain Only One Type of Object?

Question

Hey all,

Let me start with the definitions of the objects with which I am working and then I'll do my best to explain what I'm after:

class CacheItem<T> where T : EntityBase

class CacheCollection : List<CacheItem<EntityBase>>

OK, so my generic collection, CacheCollection should be a list of CacheItems which I can manipulate according to various business rules. One thing I'd like to ensure, howerver, is that each CacheCollection I instanciate only works for a single type of EntityBase. For instance, I have two classes inheriting from EntityBase; Case and Client. I'd like each CacheCollection to handle only one of those types and not mix them.

What changes can/should I make to accomodate this design requirement?

Thanks in advance, Sonny

Answer 1

You could always make CacheCollection a generic type itself and then pass that up the inheritance tree to CacheItem:

class CacheCollection<T> : List<CacheItem<T>> where T : EntityBase

Answer 2

Make CacheCollection generic, so you explicitly state the type that it can contain:

class CacheCollection<T> : List<CacheItem<T>> where T : EntityBase {}

Answer 3

It sounds like you want to get rid of CacheCollection (which serves no purpose) and have e.g.

List<CacheCollection<Case>> cases;
List<CacheCollection<Client>> clients;

no?

Answer 4

What's wrong with

class CacheCollection<T> : List<CacheItem<T>> where T:EntityBase