Question

I have the following classes / interfaces:

public interface IProjectRepository
{
    IQueryably<Project> GetProjects();
}

// Depends on my EF Context
public ProjectRepository : IProjectRepository
{
    private MyDbEntities context;

    public ProjectRepository(MyDbEntities context)
    {
        this.context = context;
    }

    public IQueryable<Project> GetProjects() 
    {
        return context.Projects;
    }
}

My controller:

 // Depends on IProjectRepository
 public class ProjectsController : Controller
 {
     private IProjectRepository projectRepository;

     public ProjectsController(IProjectRepository projectRepository)
     {
         this.projectRepository = projectRepository;
     }

     public ActionResult Index()
     {
         return View(projectRepository.GetProjects());
     }
 }

I need to set up my dependency injection so that it passes in ProjectRepository into my Controller AND it needs to pass in my Entity Framework context into the Project Repository. I need to Entity Context to be HTTP Request scoped.

I’m not sure where I am supposed to put all the mapping code to make the dependency injection work. I also don’t understand how MVC will work without the default constructor.

Can someone help me put all the pieces together? I am using StructureMap but I could easily switch to something else because I have no idea what I’m doing.

Answer 1

When using StructureMap I would generally have something like this in my controller:

private static IProjectRepository GetProjectRepository()
{
    var retVal = ObjectFactory.TryGetInstance<IProjectRepository>() 
                 ?? new ProjectRepository();
    return retVal;
}

If the TryGetInstance returns null (because nothing was set for that type) it will default to the concrete type you specify.

Now you have a bootstrapper somewhere like this:

public static class StructureMapBootStrapper
{
    public static void InitializeStructureMap()
    {
        ObjectFactory.Initialize(x =>
        {
            x.For<IProjectRepository>().Use<ProjectRepository>();
        }
    }
}

Now you call this bootstrapper in your Global.asax Application_Start event:

    protected void Application_Start()
    {
        StructureMapBootStrapper.InitializeStructureMap();
    }

Now in a test project, when you want to inject a mock repository you can just do this:

    [TestMethod]
    public void SomeControllerTest()
    {
        StructureMap.ObjectFactory.Inject(
           typeof(IProjectRepository),
           new MockProjectRepository());

        // ... do some test of your controller with the mock
    }