Question

I have a MVC3 project that uses the Entity Framework and Ninject v2.2, and follows the Unit of Work pattern with a Service Layer wrapping my repositories.

After looking at the code below, hopefully its apparent that Ninject is using constructor chaining to inject the correct classes. It currently works prefectly in my application, however I am at the point that I need to bind an instance of IDatabase to MyDatabase with a different scope such as InSingletonScope() or InNamedScope(), not InRequestScope(). I know that I can use the [Named(“MyDatabaseScope”)] Attribute to customize which IDatabase object is injected, however it seems that with my code structure, if I wanted to inject my SingletonScoped instance, I would have to recreate a new Abstract and Concrete Implementation of my Unit of Work, my Service and all my Repositories, that will then chain down.

Basically my application currently goes

Controller -> Unit of Work -> Database, (Repositories -> Database)

If I have to change my Database Binding, I will now have to create another chain in addition to the current one:

Controller -> New Unit of Work -> SingletonDatabase, (New Repositories-> SingletonDatabase)

This seems to completely defeat the DRY principal. Is there a way to, from the Controller Constructor, inform Ninject that when doing constructor chaining it should use my singleton (or named binding) rather than my request scope binding, without having to recreate all my classes with a Named attribute, or a new Interface?

Sorry for the long text, I wasnt sure if I could get the point across without my code snippets and my somewhat rambling explaination.

Ninject Module Load Function:

..snip..
Bind<IUserServices>().To<UserServices>();
Bind<IBaseServices>().To<BaseServices>();
Bind<IUserRepository>().To<UserRepository>();
Bind(typeof (IRepository<>)).To(typeof (RepositoryBase<>));
Bind<IUnitOfWork>().To<UnitOfWork>();
Bind<IDatabase>().To<MyDatabase>().InRequestScope();

//This is my problem:
//Bind<IDatabase>().To<MySingletonDatabase>().InSingletonScope();

Unit of Work Implementation Constructor:

public class UnitOfWork : IUnitOfWork
{
    private IDatabase _database;

    public UnitOfWork(IDatabase database,
                      IUserRepository userRepository,
                      IPeopleRepository peopleRepository,
        )
    {
        this._database = database;
        this.UserRepository = userRepository;
        this.PeopleRepository = peopleRepository;
    }

    protected IDatabase Database
    {
        get { return _database; }
    }

    ...snip...
}

User Service Layer Implementation Constructor:

public class UserServices : BaseServices, IUserServices
{
    private IUnitOfWork _uow;

    public UserServices(IUnitOfWork uow)
        : base(uow)
    {
        _uow = uow;
    }
    ...snip...
}

User Repository Constructor:

public class UserRepository : RepositoryBase<User>, IUserRepository
{
    public UserRepository(IDatabase database)
        : base(database)
    {
    }
    ...snip...
}

Controller Constructor:

public IUserServices _userServices { get; set; }

    public ActivityController(IUserServices userServices)
    {
        _userServices = userServices;
    }
}

Answer 1

Using Ninject 3.0.0 you can use WhenAnyAncestrorNamed("Some name") But if you need to run asyncronous things you should thing about splitting your application into a web frontend and a server backend. This could make many things easier.