DI for a Repository and Unit of Work pattern

Question

Previously I have had parameterless repositories being injected into my MVC controllers:

ProjectRepository implementation:

public class ProjectRepository : EntityFrameworkRepository<Project>, IProjectRepository
{
    public ProjectRepository()
    { }
}

UnityConfig.cs dependency resolution:

container.RegisterType<IProjectRepository, ProjectRepository>();

MVC Controller:

private IProjectRepository _projectRepository { get; set; }

public ProjectController(IProjectRepository projectRepository)
{
    _projectRepository = projectRepository;
}

This worked great.

Now I have implemented a Unit of Work pattern into my repository classes so that I can commit transactional changes to data (especially when changes are being made to more than one repository).

The new ProjectRepository implementation accepts a IUnitOfWork in its constructor:

public class ProjectRepository : EntityFrameworkRepository<Project>, IProjectRepository
{
    public ProjectRepository(IUnitOfWork unitOfWork): base(unitOfWork)
    { }
}

This means that multiple repositories can share the same IUnitOfWork and changes can be collectively committed using UnitOfWork.SaveChanges().

QUESTION:

How do I now use dependency injection to instantiate the repository with an instance of IUnitOfWork?

public ProjectController(IProjectRepository projectRepository, IUnitOfWork unitOfWork)
{
    _projectRepository = projectRepository;
    _unitOfWork = unitOfWork;
}

There could also be more than one repository injected into the controller. How can these all be instantiated with the same IUnitOfWork?

Answer 1

When you register your IUnitOfWork instance, use PerResolveLifetimeManager, this will ensure every dependency of IUnitOfWork within a single IUnityContainer.Resolve gets provided the same instance.

For example:

public class SomeDependency
{

}

public class Service
{
    public Service(SomeDependency someDependency, SomeDependency someDependency2)
    {
        Console.WriteLine(someDependency == someDependency2); 
    }
}

public static void Main()
{
    using(var container = new UnityContainer())
    {
        container.RegisterType<SomeDependency>(new PerResolveLifetimeManager());
        container.Resolve<Service>();
    }
}

This will output True to the Console.

See the page for Understanding Lifetime Managers for further details.