1. Aspect-oriented programming
robert maclean ∞

2. How is it implemented in PostSharp and how does it work?
Agenda
What, when, why of AOP?
How is it implemented in PostSharp and how does it work?
Alternatives to PostSharp
Looking to the future
Discussion

3. Every project has “boring” code
source: Microsoft Application Architecture Guide, 2nd Edition

4. Many implementations now days AKA: AOSD
AOP Details
Goal to make cross cutting concerns easy to implement and focus on business code
Xerox PARC in 2001
AspectJ
Many implementations now days
AKA: AOSD

5. Scenario code – simple prime calculator
Customer says it’s wrong. We need logging to diagnose…

6. Let’s add logging – trace input & output
Easy to miss some places
Lots of repetition of code
Need to teach this
Not portable
5 extra lines of code

7. What about some procedural help?
Not junior friendly
Need 1 per signature
15 extra lines of code

8. So how does aspects solve that?
Feel like you are missing something?
1 extra line of code

9. Demo time…

10. Under the hood
IL modified
Source: .NET Reflector 6.8

11. Many ways to implement AOP in .NET currently
Popular:
IL compile or JIT
PostSharp & Mono.Cecil
Less:
Hooking into .NET profiler API
Proxies

12. Hooking the profiler Disadvantages Poor performance
Exceptionally complex
Not designed for this
Advantages
Nothing is safe from it’s power
Solves some fringe cases (i.e. mocking static methods)
Application
COM API
Profiler
CLR
Environmental

13. Proxies Normal Proxied Method Call Method Call Object Proxy
Disadvantages
Complex with ContextBoundObject
Perf is worse than IL weaving
Advantages
Using DI it can be easier
Perf is better than .NET profiler
Object

14. Future: Post Roslyn Theory
Next version of C#/VB “compiler”
Written in managed code
Available as a service
Post Roslyn
Insert new language semantics
Approach the AspectJ style

15. AOP Way to untangle cross cutting concerns out of business code
Summary
AOP
Way to untangle cross cutting concerns out of business code
Great re-use
Can be easy to use (depending on implementation)
Many options to do this!

16. Questions & Discussions