This document discusses new features in C# 4.0 that improve productivity, including partial classes, generics, lambda expressions, extension methods, LINQ, delegates, dynamic capabilities, optional and named arguments, and better COM interoperability. It provides code examples of using dynamics, named and optional parameters, and covariance and contravariance.

1. Productivity in C# 4.0 1

2. Mohammad Tayseer 2

3. Productivity 3

4. Productivity=Value 4

5. 5 Partial Classes Object-Oriented Programming Generics C# Anonymous Types Expression Trees Lambda Expressions Extension Methods Nullable LINQ Delegates

6. C# 4.0 6

7. Dynamic capabilities Optional and named arguments Co-variant and contra-variant Better COM interoperability 7

8. Dynamic? 8

9. int x = …;x.GetType(); // Safex.SomeMethod(); // Compilation // errordynamic d = x;d.GetType(); // Safed.SomeMethod(); // Dispatched // at runtime 9

10. x.SomeMethod() x has SomeMethod x.TryInvokeMember(“SomeMethod”, …) 10

11. interface IDynamicMetaObjectProvider { boolTryGetMember(…); boolTrySetMember(…); boolTryDeleteMember(…); boolTryInvoke(…); boolTryInvokeMember(…); boolTryCreateInstance(…); boolTryGetIndex(…); boolTrySetIndex(); boolTryDeleteIndex(…); … } 11

12. 12 IronPython IronRuby C# VB.NET Others… Dynamic Language Runtime PythonBinder COMBinder ObjectBinder

13. C# 4.0 Dynamic ? 13

14. C# 4.0 Static Optional dynamic 14

15. When? 15

16. Productivity 16

17. int x = …;dynamic d = x;d.SomeMethod(); // Runtime // error 17

18.  18

19. ((MyCompany.MyClient.MyProject.Workflow.Activities.SqlSelect)this.GetActivityByName(“SqlSelect1”)).RowsAffected > 1 19

20. ((MyCompany.MyClient.MyProject.Workflow.Activities.SqlSelect)this.GetActivityByName(“SqlSelect1”)).RowsAffected > 1 20

21. ((MyCompany.MyClient.MyProject.Workflow.Activities.SqlSelect)this.GetActivityByName(“SqlSelect1”)).RowsAffected > 1 21

22. This is too complex 22

23. this.SqlSelect1.RowsAffected > 1 23 Runtime Lookup Recursive

24. ((MyCompany.MyClient.MyProject.Workflow.Activities.SqlSelect)this.GetActivityByName(“SqlSelect1”)).RowsAffected > 1this.SqlSelect1.RowsAffected > 1 24

25. dynamic x = …; x.GetType(); x.Property1 = x.Property2; x[“1”] = x[“value 2”]; x(1, 2, 3) x++; x.ExtensionMethod() // Runtime error 25

26. Dynamic DispatchDemo 26

27. Named & optional parameters 27

28. chart.ChartWizard( range.CurrentRegion, MissingValue, MissingValue, MissingValue, MissingValue, MissingValue, MissingValue, "Memory Usage in " + Environment.MachineName, MissingValue, MissingValue, MissingValue); 28

29.  29

30. chart.ChartWizard( range.CurrentRegion, // Source MissingValue, // Gallery MissingValue, // Format MissingValue, // PlotBy MissingValue, // CategoryLabels MissingValue, // SeriesLabels MissingValue, // HasLegend // Title "Memory Usage in " + Environment.MachineName, MissingValue, // CategoryTitle MissingValue, // ValueTitle MissingValue); // ExtraTitle 30

31. Strongly-typednamed parameters 31

32. chart.ChartWizard( Source: range.CurrentRegion, Gallery: MissingValue, Format: MissingValue, PlotBy: MissingValue, CategoryLabels: MissingValue, SeriesLabels: MissingValue, HasLegend: MissingValue, Title: "Memory Usage in " + Environment.MachineName, CategoryTitle: MissingValue, ValueTitle: MissingValue, ExtraTitle: MissingValue); 32

33. chart.ChartWizard( Source: range.CurrentRegion, Gallery: MissingValue, Format: MissingValue, PlotBy: MissingValue, CategoryLabels: MissingValue, SeriesLabels: MissingValue, HasLegend: MissingValue, Title: "Memory Usage in " + Environment.MachineName, CategoryTitle: MissingValue, ValueTitle: MissingValue, ExtraTitle: MissingValue); 33

34.  34

35. Optional parameters 35

36. chart.ChartWizard( Source: range.CurrentRegion, Gallery: MissingValue, Format: MissingValue, PlotBy: MissingValue, CategoryLabels: MissingValue, SeriesLabels: MissingValue, HasLegend: MissingValue, Title: "Memory Usage in " + Environment.MachineName, CategoryTitle: MissingValue, ValueTitle: MissingValue, ExtraTitle: MissingValue); 36

37. chart.ChartWizard( Source: range.CurrentRegion, Title: "Memory Usage in " + Environment.MachineName); 37

38. public void ChartWizard( Source = null, Gallery = null, Format = null, PlotBy = null, CategoryLabels = null, SeriesLabels = null, HasLegend = null, Title = “”, CategoryTitle = null, ValueTitle = null, ExtraTitle = null) 38

39. Co-variance & Contra-variance 39

40. Back to Basics 40

41. Lion is-a AnimalCamel is-a Animal 41

42. public static string CleanAnimal(Animal a) { … } CleanAnimal(camel); CleanAnimal(lion); 42

43. ThusStack<Lion>is-aStack<Animal> 43

44. No 44

45. public static string CleanAll(Stack<Animal> animals) { … } Stack<Lion> lions = { … }; CleanAll(lions); 45

46. public static string CleanAll(Stack<Animal> animals) { animals.Push(new Camel()); … } 46

47. Stack<Lion> is-notStack<Animal> 47

48. IEnumerable<Lion> should-beIEnumerable<Animal> 48

49. IEnumerable<Lion>,IEnumerator<Lion> are read-only 49

50. Only in C# 4 50

51. interface IEnumerator<out T> // T only in output position { T Current { get; } } 51

52. interface IEnumerable<out T> { IEnumerator<T> GetEnumerator(); } 52

53. Co-variance 53

54. Now Contra-variance 54

55. interface IPushable<in T> { void Push(T element); } 55

56. IPushable<Animal>is-aIPushable<Lion> 56

57. IPushable<Lion> lions = animals; lions.Push(new Lion()); IPushable<Camel> camels = animals; camels.Push(new Camel()); 57

58. Limitations 58

59. Interfaces Delegates Reference types 59

60. Co-variance & Contra-varianceDemo 60

61. BetterCOMInteroperability 61

62. Dynamic Optional & named params No PIA Omitting ref 62

63. Demos 63

64. ? 64

65. twitter.com/m_tayseerhttp://spellcoder.com/blogs/tayseerm_tayseer82@yahoo.com 65