Dependency Injection (DI) is a technique for achieving Inversion of Control (IoC) by externalizing a class's dependencies, allowing them to be injected from external sources rather than being directly hard coded. DI promotes loose coupling between classes and separation of concerns by making code depend on abstractions rather than concretions. DI can be applied through constructor injection, property injection, method injection, or ambient context. Popular DI containers include Castle Windsor, StructureMap, Spring.NET, and Ninject, which help configure and manage object lifetimes and interception.

1. Dependency Injection (DI)Or stop cooking spaghetti (code)

2. 1 “Dependency Injection is a key element of agile architecture”Ward Cunningham

3. Dependency Injection (DI) is not a pattern, but rather a set of tools2

4. DIisone of the ways to applyInversion of Control (IoC) principle3

5. Literally – let go off control and let someone feed you4

6. Example TaskObviously its time to go to code . Check out NoDI project.5

7. Specifications are singing rigoletto6

8. Specs tend to change7

9. Highly coupled code is a step to spaghetti code8Can’t intercept and change code;Can’t unit-test in isolation;Conceptual problems in modules design;Logic is spread across many parts.

10. Divide et impera9DI’s base is Interface Oriented Programming. Write your code against abstractions rather then concrete implementations.

11. Single Responsibility Principle (SRP)10By applying DI to class we let it “concentrate” on task it was designed for.

12. ModularityReplace;

13. Reuse;

14. Build in parallel;

15. Easier to maintain;

16. Easier to unit-test.Go on and check this stuff applied in PoorMansDI project.11

17. DI patterns.12

18. Composition Root13

19. Constructor injection14

20. Property (setter) injection15

21. Method injection16

22. Ambient context17

23. Which one to choose?18

24. 3D of DI19

25. 1. Composition20

26. 2. Lifetime Management21Transient (per call);

27. Singleton;

28. Per thread;

29. Per web request;

30. Per web session;