Differences Between Versions of Rx
The following topic describes the various platforms for which you can develop solutions using Reactive Extensions.
To get the latest release of Rx, as well as learn about its prerequisites, please visit the Rx MSDN Developer Center.
The core Rx interfaces, IObservable<T> and IObserver<T>, ship as part of .NET Framework 4. If you are running on .NET Framework 3.5 SP1, or if you want to take advantage of the LINQ operators implemented in Observable type, as well as many other features such as schedulers, you can download the Rx assemblies in the Rx MSDN Developer Center.
Silverlight disallows you from making cross-threading calls, thus you cannot use a background thread to update the UI. Instead of writing verbose code using the Dispatcher.BeginInvoke call to explicitly execute code on the main UI thread, you can use the factory Observable.Start method provided by the Rx assemblies to invoke an action asynchronously. Cross-threading is taken care of transparently by Rx under the hood.
You can also use the various Observable operator overloads that take in a Scheduler, and specify the DispatcherScheduler to be used.
RxJS brings similar capabilities to client script and integrates with jQuery events (Rx.Observable.FromJQueryEvent). It also supports Script#.
Windows Phone 7 ships with a version of the Reactive Extensions baked into the ROM of the device. For more information, see Reactive Extensions for .NET Overview for Windows Phone. Documentation for this version of the Reactive Extensions can be found in Windows Phone API library at Microsoft.Phone.Reactive Namespace.
The Rx MSDN Developer Center also contains an updated version of Rx for WP7, which has new definitions in the System.Reactive.Linq namespace. Note that the new APIs will not clash with the library built in to the phone (nor do they replace the version in the ROM). For more information on the differences of these 2 versions, see this Rx team blog post.