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So, I am trying to implement best practices during the design phase of a system. I am going to be using a DI container (ninject) with Entity Framework 4, ASP.NET MVC 3 C#, and the repository / unit of work pattern.

  • I am going to have models where each database's tables are mapped to classes.
  • I am going to have a connection string for each database in web.config.
  • I am going to have a class for each connection string (named the same using EF convention) which inherits from DbContext and has a DbSet for each table.
  • I am going to have an abstract repository interface for each database entity named by convention ITRepository where T is the name of the DataBase entity (ICarRepository for database entity Car). Each repository interface will hold an IQueryable for the entity and also define what methods should be exposed.
  • I am going to have a concrete repository EFTRepository which inherits from ITRepository and defines how the exposed methods work.
  • I am going to have a GenericRepository<TEntity> defined for use with entities that require only minimal access such as basic CRUD.
  • I am going to use a ControllerFactory from ninject as a DI container.
  • I am going to attach the ninject controller factory in Application_Start().
  • I am going to bind all my dependencies, such as Bind<ITRepository>().To<EFTRepository>() in the factory's AddBindings() method.
  • I am going to implement a Unit Of Work pattern for each database and keep to naming conventions UnitOfWorkDB (UnitOfWorkAutomobile for database Automobile).
  • The Unit Of Work will hold the relevant database context and repositories.

    • Am I going about this right? I haven't used this set of patterns before and want to make sure I am going to be using them correctly. Criticisms welcome!

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    • Why do you need a class for a connection string? Commented Jan 30, 2012 at 1:52
    • @Jason - that part of this is rather trivial, it is the DI, repository, and unit of work that I am trying to ensure is correct. As for the class per connection string: The class inherits DbContext, and holds a group of defined DbSet<T>. It is how Entity Framework defines a database connection and is done universally when using EF. public class DatabaseTablesExampleContext : DbContext { DbSet<SingleTableExample> SingleTableExamples; DbSet<SecondTableExample> SecondTableExamples; } Commented Jan 30, 2012 at 1:57
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      I recommend downloading the Mvc3 project called ProDinner and seeing how they made that project. It features all of the things your looking for a well thought out manner. Commented Jan 30, 2012 at 2:05
    • @SergioTapia - I checked out ProDinner, it turns out they do a couple things differently (such as Windsor instead of ninject) but they also inherit from their generic repository in their concrete ones which I thought was a great idea! Anyway, thanks for the idea, when I get more time I will look more in depth at the tutorial / code. Commented Jan 30, 2012 at 2:13

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    Inheriting from a base repository can provide some simple 'generic' functions but in other situations you'll quickly find out it becomes messy trying to have a generic based repository (assuming that was what was inheriting).

    Everything else you described seems pretty good.

    You didn't say what was going to be injected where though, I'm assuming you will be injecting a service, the service will take a unit of work (IUnitOfWork for ex., created as a per request instance) and an IWhateverRepostory

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    11 Comments

    The way I do it (using Unity but it should be basically the same) is I inject for example IEntityService (entity being whatever type) into the controller's constructor. Since I have a mapping between IEntityService and say - EntityService, the container does this automatically for me as it should for you too if you have binding declared. The service's constructor takes IUnitOfWork. IUnitOfWork is bound to my concrete implementation that inherits from DbContext. This is injected automatically as well since a binding is declared for IUnitOfWork. The service class also has in its constructor
    public EntityService(IUnitOfWork unitOfWork, IWhateverRepository whateverRepository, ISomethingElseRepository somethingElseRepository) this instantiation and injection happens automatically as well. The important thing is you inject at the controller level (your 'composition root') and everything gets filled in during the creation of that object. You'll want to ensure your objects are disposed at the end of the request (I'mnot sure with ninject what the syntax is) The best book by far on this is Manning's Dependency Injection in .Net.
    He also has a great blog as well: blog.ploeh.dk buy his book, you can't go wrong.
    Not really. Unlike most other frameworks, Unity does not scale with the number of registered types making it the slowest already for small to medium sized and larger applications. Also be aware that the IoC container takes far less than 10% of the overall processing time even for very small pages without database access making its impace almost insignificant. Rendering takes much more time so there you have a much higher optimization potential.
    See philipm.at/2011/0808 be aware that the graphs are wrong in some places becaus they are caped sometimes. See the numbers instead. But as I already mentioned I havn't seen a good post about IoC performance yet. None has multithreading, resolve of a realistic object tree (just single objects), none has a discussion about how much time is used by the IoC container in relation to the whole operation (Web, WCF request, ...) So I'd take those comparisons with a lot of caution as they look at one of many facts and are far from the reality.
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