Concurrency in C# Cookbook, 2nd Edition

Chapter 6. System.Reactive Basics

LINQ is a set of language features that enable developers to query sequences. The two most common LINQ providers are the built-in LINQ to Objects (which is based on IEnumerable<T>) and LINQ to Entities (based on IQueryable<T>). There are many other providers available, and most providers have the same general structure. Queries are lazily evaluated, and the sequences produce values as necessary. Conceptually, this is a pull model; during evaluation, value items are pulled from the query one at a time.

System.Reactive (Rx) treats events as sequences of data that arrive over time. As such, you can think of Rx as LINQ to Events (based on IObservable<T>). The main difference between observables and other LINQ providers is that Rx is a “push” model, meaning that the query defines how the program reacts as events arrive. Rx builds on top of LINQ, adding some powerful new operators as extension methods.

This chapter looks at some of the more common Rx operations. Bear in mind that all of the LINQ operators are also available, so simple operations, such as filtering (Where) and projection (Select), work conceptually the same as they do with any other LINQ provider. We won’t cover these common LINQ operations here; we’ll focus on the new capabilities that Rx builds on top of LINQ, particularly those dealing with time.

To use System.Reactive, install the NuGet package for System.Reactive into your application.

6.1 Converting .NET Events

Problem

You