ASP .NET MVC 4 - Repository dependency injection with Ninject
Repository dependency injection with Ninject
Primary Goals
First question that comes in our minds is why bother with so many layers of code. Here are the major reasons I can think off :
Maintainability and extensibility through Separations of concerns
Repository pattern enables us to separate the implementation of accessing data from the data that repositories provide.
I really like this definition:
Repositories are the single point where we hand off and fetch objects. It is also the boundary where communication with the storage starts and ends.
from Patterns of Enterprise Application Architecture, page 332.
MVC Architectural Pattern - Model/View/Controller
Code quality through Testability
Mock Repository Pattern can be used for creating mock/fake repositories. Repository mocks are useful is various ways. They enable friendly Test Driven Development, allow testing only a part of the solution, DB disconnected mode in case we do not have a DB, working on Views and Controllers without data store, etc.
Independent Unit testing for Controllers and Repositories.
Productivity through Loose coupling
Being able to work interdependently in friendly TDD environment can boost the development speed significantly. Loose coupling can be obtained with IoC and DI. We can inject dependency manually or Dependency Injection Containers such as Ninject Dependency Injector.
There is a large list of dependency containers, other better known are Unity, StructureMap, Castle Windsor and Autofac.
Solution is structured in five projects. One ASP .Net MVC4 project, one MS unit test project and three libraries. Repository contains all the "real" implementations to manipulate and expose data. MoqRepository contains fake methods together with fake/mock data. Model contains model classes. MVC project contains Controllers and Views.
ASP.Net MVC Project
Controller - just routes the calls and has no business logic inside
View - Generated with MVCScaffolding
Repository Project
Repository classes - uses DB and exposes data. EF code first strategy has been used to generate data access layer.
Repository interfaces - define the methods to be called from the Controller
Mock Repository Project
Mock repository classes - fake repository implementation. Exposes data hard-coded inside the class.
Model project
Model classes - Model classes used to define DB table and view strong typed views.
Unit test project
Test repositories - unit tests for "real" repositories
Test controllers - unit tests for Controllers.
Ninject usage
I found the most easy way to get Ninject working is through Nuget. You can install it manually but it will take more steps to finish. There is no version for MVC 4 yet but the MVC 3 version works smoothly.
Successfully added 'Ninject 3.0.1.10' to XXX.
Successfully added 'WebActivator 1.5.2' to XXX.
Successfully added 'Ninject.Web.Common 3.0.0.7' to XXX.
Successfully added 'Ninject.MVC3 3.0.0.6' to XXX.
In the App_Start project of the ASP.Net MVC project you will find a new file NinjectWebCommon.cs . All you have to do in this class is to Register services which are going to be used in Controllers:
/// <summary> /// Load your modules or register your services here! /// Uncomment line 61 to use "real" implementation /// </summary> /// <param name="kernel">The kernel.</param> private static void RegisterServices(IKernel kernel) { kernel.Load(Assembly.GetExecutingAssembly()); //kernel.Bind<IRepositoryMethods<Person>>().To<PersonRepository>(); kernel.Bind<IRepositoryMethods<Person().To<MoqPersonRepository>(); }
Loading Ninject bindings ....
and use it in the Controller, here is the example:
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