The System.Reactive.Core package includes an additional treat that can be helpful: the Rx Disposables library. It’s a set of types that implement the IDisposable interface and provides generic implementations to recurring patterns to help you accomplish most of the things you’ll need your disposable to do, without creating your own type! All the types listed in this appendix reside in the System.Reactive.Disposables namespace.
The System.Reactive.Core package is the main Rx package. For details about other Rx packages, see chapter 2.
Table B.1 will help you remember what the disposable utilities and types do.