1. Inversion of Control (IoC)
Dependency Injection (DI)
Milan Negovan

2. MILAN
NEGOVAN
ROASTS ASP.NET WITH WEB STANDARDS
ASP.NET CONSULTING SERVICES
http://aspnetresources.com
milan@aspnetresources.com

3. Example
a Contact Us web page

4. 1.Collect personal info from server controls
2.Process user's info
1. Build an email (text or HTML, in what
format?)
2.Create an SMTP client
3.Send email
3.Handle exceptions, if any
4.Anything else?
Take 1

5. 1.Collect personal info from server controls
2.Process user's info
1. Build an email (text or HTML, in what
format?)
2.Create an SMTP client
3.Send email
3.Handle exceptions, if any
4.Anything else?
Take 1

6. Cohesion
a measure of how strongly-
related and focused the various
responsibilities of a software
module are.

7. Coupling
the degree of direct knowledge
that one class has of another.

8. Strong coupling: a dependent class
contains a pointer directly to a
concrete class which provides the
required behavior.

9. Loose coupling: the dependent class
contains a pointer only to an interface,
which can then be implemented by
one or many concrete classes.

10. High cohesion: good
Loose coupling: good

11. 1.Collect personal info from server controls
2.Let something else process user's info
Take 2

12. Dependency Injection (DI)
the process of supplying an external
dependency

13. 3 elements of DI

14. Two primary approaches to DI:
constructor injection and
setter injection

15. So what is IoC about?

16. IoC is about
... looser coupling of components

17. IoC is about
... pushing dependencies outside of
your code

18. IoC is about
... less code duplication

19. IoC is about
... testing through mocking dependencies

20. IoC is about
... isolating changes

21. IoC is about
... swapping dependencies for different
environments

22. IoC is an architectural
principle
DI is its implementation.

23. Costs and benefits of unit testing
http://blog.stevensanderson.com/2009/11/04/selective-unit-testing-costs-and-benefits/
Diagram by Steve Sanderson

24. Boil WebForms down to
coordinators!

25. IoC containers for .NET
Spring.NET
StructureMap
Caslte Windsor
Unity
Managed Extensibility Framework (MEF)
Autofac

26. Demo
real-world DI

27. Group therapy
benefits and drawbacks of IoC