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Architectural Overview

CodeFirstData layer (DAL)

The data layer is the class library defining a layer which is responsible for interacting with database, contains context classes and a factory pattern implementation to interact with database. The layer contains the repository for each entity to map with database, thus making a complete ORM (Object Resource Model) solution.

CodeFirstEntities layer (POCO Model)

Entity layer acts as a model to MVC application, and is also responsible for the creation of DataBase objects when the dbset is first executed. It contains Entity classes in POCO form, having relations and data annotations(Rules/Constraints to be put on Database table/columns).

CodeFirstServices layer (BLL)

The layer contains services which uses repositories to fetch data from database. The interaction between Services and Repositories is kept loosely coupled thus implementing Inversion of Control using Dependency Injection. Its "constructor based" dependency injection does not allow service to make direct instance of our repositories. Service layer acts as an interface between controllers and repositories, passes request of controller to repositories.

Service Layer defines an application's scope and its available set of operations from the perspective of interfacing client layers. It encapsulates the application's business logic, controlling transactions and coordinating responses in the implementation of its operations.

IOC and DI

Dependency Injection is an important component in my application. All the services are required to be late bound with Model layer with Dependency Injection. In addition, the IoC container manages the lifetime of service objects. For example the Context object. I set lifetime type as PerThreadLifetimeManager in Unity configuration. This makes one and only one context object created in a single request and the different request has a different context object. Another thing I want to mention is ASP.NET MVC3 has its own way to provide Dependency Inject for controller via implementing DependencyResolver interface. The IoC container I used in the demo is Unity.

Container

The "Container" or "IOC Container" is the main object that is used to create objects and inject dependencies into them. Whenever you want an object to be open to IoC, you have to use the container to create the instance using container.Resolve<T>() method instead of the "new" keyword.

my thanks to: http://dotnetslackers.com/articles/aspnet/Code-First-Approach-using-Entity-Framework-4.aspx