This document discusses SOLID principles, dependency inversion, dependency injection, and AutoMapper. It covers the benefits of loose coupling code using dependency injection such as improved testability and separation of concerns, as well as potential downsides like increased complexity. It provides examples of dependency injection frameworks like Unity and Ninject and demonstrates how AutoMapper can simplify mapping between objects.

2. Agenda
SOLID Principles
Dependency Inversion, IoC, Dependency Injection
Pros and cons of Dependency Injection
Apply DI frameworks into MVC project
AutoMapper – What, Why and How

3. SOLID Principles
• Single Responsibility
• Open/Closed
• Liskov Substitution
• Interface Segregation
• Dependency Inversion

4. Database
Data Access Layer
Which Depends On
Business Logic Layer
Which Depends On
User Interface
Depends on
Dependencies
Lower application layers
External services
Other components

5. Example Code

6. Dependencies Inversion (Principle)
Inversion of Control (Pattern)
Service Locator Event Delegate
Dependency
Injection

7. Example Code

9. Why Dependency Injection
• Loose coupling code
• Testability
• Clear dependency
• Separate of concern
• Easy to change

10. Why NOT Dependency
Injection
• Hard to learn
• Hard to debug
• Object created before needed
• More layer => More complexity

11. Simple DI Container

12. IoC in Action
Unity
Ninject
Structure Map

13. What
An “object to object”
mapper
Why
Remove the boring
mapping code
When
Entity to DTO
Entity to Data Contact
Entity to View Model

14. Before and after

15. Mapper in Action