Onion Architecture, Unit of Work and a generic Repository pattern

This is the first time I am implementing a more domain-driven design approach. I have decided to try the Onion Architecture as it focuses on the domain rather than on infrastructure/platforms/etc.

In order to abstract away from Entity Framework, I have created a generic repository with a Unit of Work implementation.

The IRepository<T> and IUnitOfWork interfaces:

public interface IRepository<T>
{
    void Add(T item);

    void Remove(T item);

    IQueryable<T> Query();
}

public interface IUnitOfWork : IDisposable
{
    void SaveChanges();
}

Entity Framework implementations of IRepository<T> and IUnitOfWork:

public class EntityFrameworkRepository<T> : IRepository<T> where T : class
{
    private readonly DbSet<T> dbSet;

    public EntityFrameworkRepository(IUnitOfWork unitOfWork)
    {
        var entityFrameworkUnitOfWork = unitOfWork as EntityFrameworkUnitOfWork;

        if (entityFrameworkUnitOfWork == null)
        {
            throw new ArgumentOutOfRangeException("Must be of type EntityFrameworkUnitOfWork");
        }

        dbSet = entityFrameworkUnitOfWork.GetDbSet<T>();
    }

    public void Add(T item)
    {
        dbSet.Add(item);
    }

    public void Remove(T item)
    {
        dbSet.Remove(item);
    }

    public IQueryable<T> Query()
    {
        return dbSet;
    }
}

public class EntityFrameworkUnitOfWork : IUnitOfWork
{
    private readonly DbContext context;

    public EntityFrameworkUnitOfWork()
    {
        this.context = new CustomerContext();;
    }

    internal DbSet<T> GetDbSet<T>()
        where T : class
    {
        return context.Set<T>();
    }

    public void SaveChanges()
    {
        context.SaveChanges();
    }

    public void Dispose()
    {
        context.Dispose();
    }
}

The Customer repository:

public interface ICustomerRepository : IRepository<Customer>
{

}

public class CustomerRepository : EntityFrameworkRepository<Customer>, ICustomerRepository 
{
    public CustomerRepository(IUnitOfWork unitOfWork): base(unitOfWork)
    {
    }
}

ASP.NET MVC controller using the repository:

public class CustomerController : Controller
{
    UnityContainer container = new UnityContainer();

    public ActionResult List()
    {
        var unitOfWork = container.Resolve<IUnitOfWork>();
        var customerRepository = container.Resolve<ICustomerRepository>();

        return View(customerRepository.Query());
    }

    [HttpPost]
    public ActionResult Create(Customer customer)
    {
        var unitOfWork = container.Resolve<IUnitOfWork>();
        var customerRepository = container.Resolve<ICustomerRepository>();; 

        customerRepository.Add(customer);

        unitOfWork.SaveChanges();

        return RedirectToAction("List");
    }
}

Dependency injection with unity:

container.RegisterType<IUnitOfWork, EntityFrameworkUnitOfWork>();
container.RegisterType<ICustomerRepository, CustomerRepository>();

Solution:

PROBLEMS?

• Repository implementation (EF code) is very generic. It all sits in side the EntityFrameworkRepository<T> class. Concrete model repositories do not contain any of this logic. This saves me from writing tons of redundant code, but possibly sacrifices flexibility?

• The ICustomerRepository and CustomerRepository classes are basically empty. They are purely there to provide abstraction. As far as I understand, this fits with the vision of the Onion Architecture, where infrastructure and platform-dependent code sits on the outside of your system, but having empty classes and empty interfaces feels wrong?

• To use a different persistence implementation (say Azure Table Storage), then a new CustomerRepository class would need to be created and would inherit a AzureTableStorageRepository<T>. But this could lead to redundant code (multiple CustomerRepositories)? How would this effect mocking?

• Another implementation (say Azure Table Storage) has limitations on transnational support so the a AzureTableStorageUnitOfWork class wouldn't work in this context.

Are there any other issues with the way I have done this?

(I have taken most of my inspiration from this post)