Slides from my presentation on Functional Alchemy at DDD SouthWest (and other places)

1. Functional Alchemy Tricks to keep your C# DRY Mark Rendle Principal Architect Dot Net Solutions @markrendle

2. Get all the code:bit.ly/functionalalchemy(bitbucket.org)

3. Functional?

4. First-class functions

5. Action<T>Func<T, Tresult>

6. Higher-order functions

7. Lazy evaluation

8. Immutability

9. Purity

10. Tail-call optimisation

11. So, C# then It's an Object Oriented language

12. Object Orientation When all you've got is a hammer…

13. Object Orientation …everything looks like nails

14. Demo:WPF Commands

15. Tuples

16. Tuple<T1,T2>

17. F# TryParse success, i = int.TryParse(“42”)

18. C# TryParse int i;bool success = int.TryParse(“42”, out i);

19. C# TryParse var tuple = IntTryParse(“42”);if (tuple.Item1) { ... }

20. Demo:Tuple extensions

21. Fixing C# and .NET (because it’s borked)

22. var handler = MyEvent;if (handler != null){handler(this, EventArgs.Empty);}

23. Demo:EventHandler.Raise

24. ImprovingException Handling

25. try{File.OpenRead(“foo.txt”);}catch (FileNotFoundException ex){Error(ex.Message);}catch (DirectoryNotFoundException ex){Error(ex.Message);}catch (UnauthorizedAccessException ex){Error(ex.Message);}

26. Demo:Multi-exception Catch

27. Augmentingfunctions

28. Demo:Caching deterministicmethods

29. “Event-based Async Pattern” void ClickHandler() { SomeService.MethodCompleted += CompletedHandler; SomeService.MethodAsync(); } void CompletedHandler(object sender, MethodCompletedEventArgs e) { // Do something with e }

30. Demo:Event-based AsyncPattern implementation

31. Function Composition

32. Demo:Composing Cachingand Async Pattern

33. That’s it. Download the code: bit.ly/functionalalchemy Further reading: LINQ to Objects Using C# 4.0 (Magennis) Real World Functional Programming (Petricek/Skeet) Actual functional programming: Learn F#