Review of old topic regarding dependency injection. Why it's still important and actual in the industry. Will look into more depth of this is handled in Episerver and related libraries.

2. Dependency Injection
in Episerver

4. Dependency Injection
in .Net

6. wałdis iljuczonok (aka technical fellow)
tech guy at getadigital.com
(Microsoft .Net + Episerver) ◦ MVP
@tech_fellow

7. Why?

8. Testability

10. @tech_fellow
What is dependency?

11. public class Class1
{
public Class1()
{
}
public Answer Method1(string directory)
{
// ....
return ...;
}
}

12. @tech_fellow
«DI is a set of principles and patterns that enable loose
coupling* »
* - http://blog.ploeh.dk/2010/04/07/DependencyInjectionisLooseCoupling/

13. @tech_fellow
s.o.l.i.d.

14. @tech_fellow
s.o.l.i.d.

15. Patterns

16. public class Class1
{
private readonly ISomeService _service;
public Class1(ISomeService service)
{
_service = service;
}
public IAnotherService AnotherService { private get; set; }
public Answer Method1(IThirdService thridService)
{
return thridService.CouldBe() ? Answer.Yes() : Answer.No();
}
}
Constructor Injection
Property Injection
Method Injection

17. public static class AmbientContext
{
public static ISomeService TheService { get; } = new SomeService();
}
Ambient Context

19. @tech_fellow
Composition Root

20. Layered

21. Onion

22. hexagonal

23. pizza

24. @tech_fellow
Main(string[] args)
Global.asax & IControllerFactory
Startup.cs & RouterMiddleware
..rely on framework..

25. @tech_fellow
IConfigurableModule
IInitializableModule*

26. Anti-Patterns

27. @tech_fellow
Control Freak

28. public class Class1
{
private readonly ISomeService _service;
public Class1(ISomeService service)
{
_service = service;
}
public IAnotherService AnotherService { private get; set; }
public Answer Method1(IThirdService thridService)
{
return thridService.CouldBe() ? Answer.Yes() : Answer.No();
}
}

29. public class Class1
{
private readonly ISomeService _service;
public Class1()
{
_service = new SomeService();
}
public IAnotherService AnotherService { private get; set; }
public Answer Method1()
{
var thridService = new ThirdService();
return thridService.CouldBe() ? Answer.Yes() : Answer.No();
}
}

30. @tech_fellow
Control Freak
Bastard Injections

31. public class Class1
{
private readonly ISomeService _service;
public Class1()
{
_service = new SomeService();
}
public IAnotherService AnotherService { private get; set; }
public Answer Method1()
{
var thridService = new ThirdService();
return thridService.CouldBe() ? Answer.Yes() : Answer.No();
}
}

32. public class Class1
{
private readonly ISomeService _service;
public Class1(ISomeService service)
{
_service = service;
}
public Class1()
{
_service = new SomeService();
}
public IAnotherService AnotherService { private get; set; }
public Answer Method1()
{
var thridService = new ThirdService();
return thridService.CouldBe() ? Answer.Yes() : Answer.No();
}
}

33. @tech_fellow
Control Freak
Bastard Injections
Constrained Construction

35. @tech_fellow
Control Freak
Bastard Injections
Constrained Construction
Service Locator

38. [Fact]
public void TestMethod1()
{
var kpi = new Kpi();
kpi.Evaluate(this, new EventArgs());
...
}

39. @tech_fellow

41. @tech_fellow
T Injected<T>
T ServiceAccessor<out T>

43. Don’t ask, we will call you!
Hollywood Principle

44. DI in Episerver

45. @tech_fellow
Scheduled Jobs

46. @tech_fellow
Configurable Modules
&
Initializable Modules

47. @tech_fellow
Episerver Forms Actors

49. @tech_fellow
Razor Page*

50. @tech_fellow
Extension Methods

51. @tech_fellow
Episerver Developer Tools AddOn

52. DI Friendly Libraries

53. @tech_fellow
Libraries are designed to be «consumed»

54. @tech_fellow
Conforming Container
(anti-pattern)

55. @tech_fellow
FeatureSwitch

56. *.Ninject
*.StructureMap
*.Unity
*.<your-container>

57. *.Ninject
*.StructureMap
*.Unity
*.<your-container>

58. @tech_fellow
AbstractFactory

59. public delegate object SingleInstanceFactory(Type target);
public class TypeAbstractFactory
{
private readonly SingleInstanceFactory _factory;
public TypeAbstractFactory(SingleInstanceFactory factory)
{
_factory = factory;
}
private void CreateTargetType()
{
var s = (ISomeService)_factory(typeof(ISomeService));
}
}

60. context.Container.Configure(
c => c.For<SingleInstanceFactory>()
.Use<SingleInstanceFactory>(ctx => ctx.GetInstance));

61. public delegate object SingleInstanceFactory(Type target);
public class TypeAbstractFactory
{
private readonly SingleInstanceFactory _factory;
public TypeAbstractFactory(SingleInstanceFactory factory)
{
_factory = factory;
}
private void CreateTargetType()
{
var s = (ISomeService)_factory(typeof(ISomeService));
}
}

62. @tech_fellow
Constructor Over-Injection

63. DI Friendly Framework

64. @tech_fellow
[ServiceConfiguration( … )]

66. @tech_fellow
RRR
Register-(Resolve-Release)

67. public delegate object SingleInstanceFactory(Type target);
public class TypeAbstractFactory
{
private readonly SingleInstanceFactory _factory;
public TypeAbstractFactory(SingleInstanceFactory factory)
{
_factory = factory;
}
private void CreateTargetType()
{
var s = (ISomeService)_factory(typeof(ISomeService));
}
}

68. @tech_fellow
Remember to Release

69. Extra Bonus with DI

70. @tech_fellow
Aspects
(Interceptors & Decorators)

71. russian doll model
https://cynthianewberrymartin.files.wordpress.com/2009/05/blog-2-13.jpg

72. @tech_fellow
Validation
Pre/post processing
Authorization
Logging
Auditing
Event dispatching
Notifications
Unit of work/transactions
...

73. @tech_fellow
Create loose-coupling code
Demand dependencies from consumer
Leverage DI container features
Look for anti-patterns

74. @tech_fellow
Be a BOY SCOUT!