Good introduction to the .NET Reactive Framework

Question

Aside from the Microsoft documentation, is there a good introduction and tutorial to the Microsoft Reactive (Rx) framework?

Also, what is a good example (with code) that Reactive makes easier of a programming problem that is challenging to solve using conventional asynchronous coding techniques?

I keep looking - I'll need to see a lot of examples before I have a good idea what it's best used for. — Sam Harwell, Oct 20 '09 at 17:45
I built a small demo of live Bing search in WPF with Rx : http://blog.andrei.rinea.ro/2013/06/01/bing-it-on-reactive-extensions-story-code-and-slides/ — Andrei Rînea, Jun 01 '13 at 20:47
I answer exactly this question in a series of posts on my blog: http://rehansaeed.co.uk/reactive-extensions-part1-replacing-events/ — Muhammad Rehan Saeed, Sep 24 '14 at 12:53

score 103 · Answer 1 · edited Dec 24 '16 at 08:11

103

UPDATE: The blog posts below have been superseded by my online book www.IntroToRx.com. It is a comprehensive 19 chapter book available for free. You can browse it on the web, or download the mobi version for your kindle. You can also get it direct from Amazon for a tiny fee (~99c / 77p). If the book doesn't meet your needs or expectations, let me (the Author) know and we will do better for v2.

Thanks for the link to the Hot/Cold post. This is only one part of the full series,

Introduction to Rx
Static and extension methods
Lifetime management – Completing and Unsubscribing
Flow control
Combining multiple IObservable streams
Scheduling and threading
Hot and Cold observables
Testing Rx
Buffer, Window, Join and Group Join

I will keep updating this blog with more Rx introductory stuff.

For more advanced stuff you want to go to the Rx Forum (MSDN).

edited Dec 24 '16 at 08:11

C2H6O

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answered Jan 04 '11 at 14:51

Lee Campbell

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I've been dragging my feet learning about Rx because all of the learning materials are in the form of videos. +1 for providing this text-based resource. – Daniel Schilling Jan 08 '14 at 19:44
Enumerate this link is dead. – Maslow Sep 22 '16 at 20:39
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Long live Enumerate this link – Full Time Skeleton Jan 12 '17 at 14:13
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I work with James (EnumerateThis) and he just hasn't touched it in years. He doesn't seem to have the time or appetite to revive it – Lee Campbell Jan 12 '17 at 21:17

score 85 · Accepted Answer · edited Feb 13 '12 at 15:20

85

Here's a wiki site with lots of code examples demonstrating how to use different features of the .NET Rx framework: http://rxwiki.wikidot.com/101samples

I found this to be the most comprehensive site out there, and the one that's quickest to get started with.

edited Feb 13 '12 at 15:20

bernhof

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answered Dec 23 '09 at 02:30

LBushkin

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So far as I can tell this wiki doesn't so much as tell you which reference to include. Which is rather...frustrating. – George Mauer Sep 15 '10 at 14:07
umm just add the dlls and open object explorer and search for the class. of course the right click context menu in Visual studio helps too – Joe Nov 20 '12 at 03:41

Summer-Time · Answer 3 · 2021-07-30T08:00:54.033

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MSDN Site for Rx-Framework

For a Developer going deeper, the Source Code

Cool Austrian keynote about Rx

This is the best I have seen: DevCamp 2010 Keynote - Rx: Curing your asynchronous programming blues

Some interesting Videos on Channel 9

Kim Hamilton and Wes Dyer: Inside .NET Rx and IObservable/IObserver in the BCL (VS 2010)

An interview with the creator from Rx: Expert to Expert: Brian Beckman and Erik Meijer - Inside the .NET Reactive Framework (Rx)

An introduction from the creator of Rx

An Codeproject Article

Another course first blog with links (new)

edited Jul 30 '21 at 08:00

answered Nov 18 '09 at 10:55

Summer-Time

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+1 Highly recommend these videos, I learned a LOT, also check out some of Bart De Smet 's videos on IQueryable and IQbservable, You get a better understand of the insides of Rx. – gideon Jan 14 '11 at 16:43
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The complete samples project for the "DevCamp 2010 keynote" video is here: http://www.bartdesmet.net/download/Rx40Samples.zip – Omer Raviv Jan 20 '11 at 09:15

score 16 · Answer 4 · answered Nov 17 '09 at 14:26

16

Here's an example of something that is easy to do with reactive programming, but messy (if not challenging) with classic events, it draws lines while the mouse button is down. It is readable, there is no explicit state handling:

var pen = new Pen(Color.Red, 3);
var graphics = this.CreateGraphics();

var mouseMoveWhileDown = 
    from md in this.GetMouseDown()
    from mv in this.GetMouseMove().Until(this.GetMouseUp())
    select new Point(mv.X, mv.Y);

mouseMoveWhileDown
    .Pairwise()
    .Subscribe(tup => graphics.DrawLine(pen, tup.Item1, tup.Item2));

(I must confess that in that example, Pairwise() is home-grown...)

The most important thing about IObservable is that it is 'composable', just like IEnumerable.

I thouroughly recommend the video mentioned in another answer. In fact there are several different videos on the subject on Channel9:

answered Nov 17 '09 at 14:26

Benjol

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Where does .Until come from, I can never use it, I must be missing a reference – TimothyP Sep 20 '10 at 17:27
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@TimothyP, I think it might be a throwback to an older version. That or I wrote one myself (I was playing with implementing IObservable extension methods at the time). From what I can see, the latest version of reactive extensions has a method called `TakeUntil`, which looks like a good fit. – Benjol Sep 21 '10 at 04:58
This is an awesome example that shows the spirit of Rx. Thanks. – Dan Abramov Jul 25 '11 at 15:48
Can you share the implementation of Pairwise()? – blaster Feb 27 '13 at 16:08
Ooh, @blaster, that's a tough question. I'll see if I can find it, and failing that, I'll see if my rusty brain can recreate it! – Benjol Feb 28 '13 at 05:58
@blaster, I've got something, why don't you post another question and ping me with the link? – Benjol Feb 28 '13 at 07:52
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@blaster, how about this implementation: `var pairwise = source.Zip(source.Skip(1), (x, y) => new Tuple(x, y))`. – MisterMetaphor Feb 04 '14 at 16:38

score 12 · Answer 5 · edited Sep 15 '10 at 11:17

12

Once you have gone through some of the basic stuff including the HandsOnLab make sure you check out Lee Campbell's Hot and Cold Observables which took some of the arcane mystery out of Rx for me :)

edited Sep 15 '10 at 11:17

Oliver

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answered Sep 15 '10 at 10:46

sweetlilmre

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Colonel Panic · Answer 6 · 2012-06-13T10:21:34.350

Bizarrely, the Reactive Extensions homepage links to a dozen videos and blogs but forgets to link to the comprehensive official reference documentation. That's a crying shame, if you know the team, please ask them to fix their website!

score 4 · Answer 7 · edited Oct 02 '11 at 08:48

4

You may find this series of articles (there are four) about reactive LINQ useful: Reactive programming (II.) - Introducing Reactive LINQ.

He has an example of writing a game using it, so it should hopefully be what you are looking for.

edited Oct 02 '11 at 08:48

Peter Mortensen

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answered Oct 20 '09 at 17:37

James Black

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score 4 · Answer 8 · edited Oct 02 '11 at 08:49

4

I also found Introducing the Reactive Framework Part I on CodeBetter.com. There is a sequel to the first part on the same site.

I hope this will help you.

edited Oct 02 '11 at 08:49

Peter Mortensen

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answered Nov 03 '09 at 12:21

FrenchData

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score 3 · Answer 9 · answered Jan 21 '11 at 11:33

3

Play with Rx Sandbox to get a very intuitive view of what the different combinators mean. This is the best learning tool I've seen.

answered Jan 21 '11 at 11:33

Omer Raviv

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score 2 · Answer 10 · answered Nov 18 '09 at 14:40

Go through these articles, and in particular, download the related source code and play with it.

Part I - System.Reactive or the .NET Reactive Extensions (Rx) – Concepts and First Look
Part II - LINQ To Events - More on .NET Reactive Extensions (Rx)
Part III - LINQ To Events - Generating GetEventName() Wrapper Methods using T4 Text Templates

Trust this will help

score 2 · Answer 11 · edited Oct 02 '11 at 09:08

To answer the second question, here is a problem that can benefit a lot from Rx. It's called "Get rich quick".

You have developed a game by the same name and it's selling pretty well. But it is available only at your stores for wholesale. To make the cash processing easier, you have a conveyor belt which flows towards you.

(Please feel free to change the story above :) )

Sales people place bound wads of cash on it with no labels indicating the amount and type of bills in the wad. Your job is to sort and count the money. Later on, when you get more money, you can hire others to help you.

In this case, the source is an asynchronous source of wads of cash (Producer). Your employees and suppliers expect money, but you have to consume the wads, unpack them and use your custom business logic to repackage as appropriate to pay them.

The sales people are running on their own thread, so that they don't have to wait for you to count what they throw on the belt. Your time is best utilized if you are told when more money is available to count, until then you can do other work.

You could represent each wad by a byte[].

This is a fairly common real world situation; when you retrieve any resource [for example, webpages for search engines, images or videos] on a network or data from peripherals, you get them in chunks of bytes (possibly with headers). In a single thread, or in a multi-thread environment that is too difficult to work with, you tend to aggregate and process them. Not any more!!

this is just some producers (sales people) calling OnNext on the same IObserver and then the consumer subscribing but ensuring that the it is Observing on a different thread to where it is being produced(OnNext). — Lee Campbell, Apr 22 '11 at 16:11

score 2 · Answer 12 · answered Nov 06 '11 at 05:33

2

Jesse Liberty has a book out, published Oct 2011:

Amazon.com: Programming Reactive Extensions and LINQ

And there's the RxWorkshop videos on Channel9:

Channel9: RxWorkshop

answered Nov 06 '11 at 05:33

Shane Castle

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Matt Breckon · Answer 13 · 2009-11-17T22:02:17.903

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Does your "excluding Microsoft documentation" clause extend to the videos on Channel 9?

From the creator of the reactive framework Erik Meijer: - Expert to Expert: Brian Beckman and Erik Meijer - Inside the .NET Reactive Framework (Rx)

Brand new: Getting Started with Rx Extensions for .NET

edited Nov 17 '09 at 22:02

answered Oct 31 '09 at 13:50

Matt Breckon

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also http://channel9.msdn.com/shows/Going+Deep/Kim-Hamilton-and-Wes-Dyer-Inside-NET-Rx-and-IObservableIObserver-in-the-BCL-VS-2010/ – Matt Breckon Oct 31 '09 at 13:50

score 1 · Answer 14 · edited Oct 02 '11 at 09:04

1

DEVHOL202 – Curing the asynchronous blues with the Reactive Extensions for .NET (PDF, 2 MB) is the best lab/tutorial I've seen so far. It guides you through the basics of the library, so that you can build and design on what you've learned.

There is also a JavaScript version. Search Google for "Reactive Extensions Hands on Lab".

edited Oct 02 '11 at 09:04

Peter Mortensen

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answered Jan 08 '11 at 07:53

John C

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score 1 · Answer 15 · answered Jan 14 '11 at 16:49

In addition to Andreas Hoffmann's links (found them very helpful when I was learning Rx)

Here are some of Bart De Smet (a VERY smart guy who explains things really well) Videos:

Kinda a run through of Rx:
Rx - Curing your Asynchronous Programming Blues

Some gory insides + some philosophy, these videos are really enlightening:
Min LINQ - The essence of LINQ
(The above video deals with how LINQ kinda relates to other things, Like Rx)

Observations on IQbservable - The Dual of IQueryable

score 0 · Answer 16 · edited Oct 02 '11 at 09:16

0

I liked Introduction to Rx Part 1 - Key types, and it showed the key features.

edited Oct 02 '11 at 09:16

Peter Mortensen

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answered Jul 08 '11 at 13:22

vidalsasoon

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this series evolved into online book at http://www.introtorx.com/ – voidengine Jul 25 '12 at 19:06

Good introduction to the .NET Reactive Framework

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