ASP.NET MVC应用程序和依赖项注入的适当分层

Question

I have a project that has three layer.

1st is the DAL

2nd is the Domain

3rd is the Presentation

I created an interface in my Domain Layer (ICategoryRepository) here is the Code

public interface ICategoryRepository
{
    List<CategoryDTO> GetCategory();
}

and I created a class in my DAL to implement the ICategoryRepository in my Domain.

public class CategoryRepository : ICategoryRepository
{                     
    BookInfoContext _context;

    public List<CategoryDTO> GetCategory()
    {
        _context = new BookInfoContext();

        var categoryDto = _context.Categories
                            .Select(c => new CategoryDTO
                            {
                                CategoryId = c.CategroyId,
                                CategoryName = c.CategoryName
                            }).ToList();
        return categoryDto;
    }
}

Then I create a class in my Domain and pass the ICategoryRepository as parameter in my constructor.

public class CategoryService
{

    ICategoryRepository _categoryService;

    public CategoryService(ICategoryRepository categoryService)
    {
        this._categoryService = categoryService;
    }

    public List<CategoryDTO> GetCategory()
    {
        return _categoryService.GetCategory();
    }
}

I do this to invert the control. Instead of my domain will depend on DAL I invert the control so that myDAL will depend on my DOMAIN.

My Problem is, everytime I call the CategoryService in the Presentation Layer I need to pass ICategoryRepository as parameter of constructor which is in the DAL. I don't want my Presentation Layer to be dependent in my DAL.

Any suggestion?

Thanks,

Answer 1

You could use a dependency injection. In asp.net mvc we have a IDepencyResolver interface that inject dependencies on controllers dependencies and its dependencies. To do this, you will need a container to be easy to inject your dpendencies, for sample, MS Unity, Ninject, etc.. and register all types on your container to it knows how to resolve your dependencies.

With a Container and DependencyResolver setted, you can have a dependency of your service on your controller , for sample:

public class CategoryController
{
   private readonly ICategoryService _categoryService;

   // inject by constructor..
   public CategoryController(ICategoryService categoryService)
   {
       _categoryService = categoryService;
   }


   public ActionResult Index()
   {
      var categories = _categoryService.GetCategory();

      return View(categories);
   }

}

In this case, the Container will see the controller need the service and this service need a repository. It will resolve everything for your, since your have registred these types.

Take a look at this article: http://xhalent.wordpress.com/2011/01/17/using-unity-as-a-dependency-resolver-asp-net-mvc-3/