.NET 4.0 introduced a pair of interfaces, IObservable<T> and IObserver<T>, supporting subscriptions to and notifications for push-based sequences. In combination with Reactive Extensions (Rx), these interfaces provide a convenient and uniform way of describing event sources and sinks in .NET. The StreamInsight CTP refresh in November 2009 included an Observable adapter supporting “reactive” event inputs and outputs.

While we continue to believe it enables an important programming model, the Observable adapter was not included in the final (RTM) release of Microsoft StreamInsight 1.0. The release takes a dependency on .NET 3.5 but for timing reasons could not take a dependency on .NET 4.0. Shipping a separate copy of the observable interfaces in StreamInsight – as we did in the CTP refresh – was not a viable option in the RTM release.

Within the next months, we will be shipping another preview of the Observable adapter that targets .NET 4.0. We look forward to gathering your feedback on the new adapter design! We plan to include the Observable adapter implementation into the product in a future release of Microsoft StreamInsight.