1. Yann Schwartz - Polom
Pierre Couzy – Microsoft
WebWorkersCamp, 30/10/2010

2. Yann :
 .Net heretic (@abolibibelot)

3. Pierre :
 Worked in the Microsoft space for 20 years
 Speaker, trainer, developer, architect, …
 Primarily interested inWeb topics
 Identity, architecture,WS-*, interop, cloud, …
 Recent interop/OSS activity
 Worked on drupal for Sql server project
 Works on automated drupal testing onWindows
 Speaker at major PHP events
▪ DrupalCon, PHP Forum, Symfony live
blog.couzy.com / pierre.couzy@microsoft.com

4. A little syntactic sugar can help you think along
the right lines

5.  C# is an imperative language
 Which is nice
 Except for a few things
 Splitting data manipulation between your code
and your data store
 Coding data manipulation
 Applying new manipulation patterns to existing
data

7.  Express more intent, less implementation
 Easy composition
 Strong typing
 This is subject to hot debate
 .. And out of scope today
 Be as declarative as possible within the limits
imposed by an imperative language

9.  Lazy evaluation
 If we step into this code, we see LINQ triggers its magic on
demand
 Easy composition
 If we add new clauses after the LINQ expression is built
but before it’s consumed, we simply merge the additions
to the existing expression
 So far, we’ve worked on objects
 Which is how many naive LINQ implementations work :
synchronously pipelining methods calls on collections
 LINQ has a lot more to it
 But this not on our todo today

10. A lazy,pull-based,composable pattern for data
manipulation
And we get

11.  Imperative synchronous programming was
hard enough to call for LINQ
 And yet we’ve been doing this for decades
 Event-based (or async) patterns are a
complete mess today
 Unconvinced ? Let’s see…

12.  We were pulling data from an enumerable
 We will push data from an observable
 We were lazy (doing just in time)
 We will receive data as a stream (just in time)
 We were composable
 We’ll stay that way

13.  It’s a source
 Our code will subscribe to that source
 Duh, difference with an event handler ?
 Observable sequences are first-class
constructs
 Provide a layer of abstraction
 Much better for testing
 Allows for much more scenarios

14.  A sequence is more than a list of ..
 It can fail
 It can end
 The observer , when it subscribes, can
subscribe to those three conditions

15.  Observables allow you to manipulate a
chronology of events as a list.
 And we can apply operators to lists.
 This is called a workflow.

16.  LINQ describes an iteration workflow (pull-
based), with composition, so that the
implementation does not obfuscate the
intention,
 Rx describes an event-based workflow (push-
based), with composition, so that the
implementation does not obfuscate the
intention.