This document discusses aspect-oriented programming (AOP) and how it can be implemented using PostSharp. AOP aims to make cross-cutting concerns like logging and error handling easier to implement separately from business logic. It describes how PostSharp uses IL weaving to modify code at compile time or JIT to add aspects without changing the original code. Alternatives to PostSharp include using the .NET profiler API or proxies, but IL weaving generally has better performance. The document also briefly outlines how AOP may be improved in future versions of C# compilers like Roslyn.

1. Aspect-oriented programming robertmaclean www.sadev.co.za ∞ @rmaclean ∞ robert@sadev.co.za

2. 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. 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 Source: .NET Reflector 6.8 IL modified

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

12. IL Weaving .cs or .vb code IL (pure) PostSharp IL (Merged)

14. Exceptionally complex

16. Solves some fringe cases (i.e. mocking static methods)Application COM API CLR Profiler Environmental

19. Perf is better than .NET profilerObject

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

21. 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!

22. Questions & Discussions