Concurrency in C# Cookbook

Chapter 5. Rx 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 (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.

Reactive Extensions (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. This means 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.

In this chapter, we’ll look 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. This chapter will not cover these common LINQ operations; it focuses on the new capabilities that Rx builds on top of LINQ, particularly those dealing with time.

To use Rx, install the NuGet package Rx-Main into your application. Reactive Extensions has wide platform support (Table 5-1):

Table 5-1. Platform ...