MVC 3: Injecting multiple repositories into a single controller

Question

My presentation layer is in MVC 3.

I have a data access layer which returns repositories. Each repository is mapped to a single table.

For example, I have the following repository interfaces:

ICustomerRepository
ICustomerTypeRepository

I have Entity Framework implementations of these repositories. These implementations get injected at a runtime with Ninject.

I have two controllers:

CustomerController
CustomerTypeController

Each controller has a set of CRUD routines. Customer must have a type.

In order to create a customer record, I need to use EFCustomerTypeRepository.

I now have a constructor within a CustomerController which looks this:

public class CustomerController: Controller
{
   private ICustomerRepository customerRepository;        
   private ICustomerTypeRepository customerTypeRepository; 

   public CustomerController(ICustomerRepository customerRepository, 
                             ICustomerTypeRepository customerTypeRepository)
   {
      this.customerRepository = customerRepository;            
      this.customerTypeRepository = customerTypeRepository;
   }     

...

Development is in early phase, and if I take this approach, then within next few days this constructor will have 5 or more parameters. This doesn't look right.

I could store all this logic in EFCustomerRepository, however, this will break single responsibility principle. So I'm not going to do that.

Finally, I can wrap these repositories and pass a single RepositoryWrapper type object to my controller.

I don't want to introcude any more frameworks, tools than I have to. I'm aiming to achieve loose coupling and easy extensibility, but currently I'm stuck between passing more parameters to a constructor, or writing a wrapper for repositories.

I'm using MVC 3, EF 4.1, Ninject, Moq and Automapper. Thank you

possible duplicate of [Dependency Injection Constructor Madness](http://stackoverflow.com/questions/2420193/dependency-injection-constructor-madness) — Mark Seemann, Aug 16 '11 at 15:32

score 2 · Accepted Answer · answered Aug 16 '11 at 19:03

2

I would say you have to watch for aggregates in your code (from Domain Driven Design point of view). So if you can make a class encapsulate a lot of small other classes for which there's no use storing them by themselves you can create a nice objectgraph and having just a single ICustomerRepository which encapsulates the internal references to for example customer type.

answered Aug 16 '11 at 19:03

thekip

3,660
2
21
41

Ended up writing an aggregate to wrap my repositories into a single service. – Aug 30 '11 at 09:35

score 0 · Answer 2 · edited Oct 20 '12 at 01:59

0

Anyway, injecting multiple repositories into a controller constructor isn't necessarily a bad practice. It is called "constructor over-injection", see Mark Seemann's book on this topic.

edited Oct 20 '12 at 01:59

McGarnagle

101,349
31
229
260

answered Jun 18 '12 at 10:54

Alessandro

61
6

MVC 3: Injecting multiple repositories into a single controller

2 Answers2