A CollectionView is created if your source implements IEnumerable. If the source implements IEnumerable *only*, you will not be able to sort or group the collection (you can only filter it). Also, perf will not be the best if the source has a large number of items or if you perform dynamic operations such as insertions and deletions. If this is your scenario, you should consider having your source implement a stronger interface. ICollection is slightly better because it provides a Count property.