使用Unity和asp.net mvc对数据库操作进行依赖注入

Question

I'm trying to integrate dependency injection by employing unity container in an ASP.NET MVC app. In the spirit of loose coupling, I apply constructor injection on my controller and my product data access class. This is a glimpse of the code :

public interface IProduct
{
   IEnumerable<Product> findAll();
   Product find(Guid id);
   void create();
}
public class Product()
{
    public Guid id { get; set; }
    public string name { get; set; }
    public decimal price { get; set; }

    //dependency
    private IDBEngine _engine = null;

    public Product(IDBEngine engine) {
        this._engine = engine;
    }

    public IEnumerable<Product> findAll() {
        using(IDBconnection connection = this._engine.getConnection()) 
        {
            connection.open();

            //implementation of fetching all datas from db

            return datas;
        }
    }

    public Product find(Guid id) {
        using(IDBconnection connection = this._engine.getConnection()) 
        {
            connection.open();

            //implementation of fetching single data given id from db

            return data;
        }
    }

    public void create(Product product) 
    {
        using(IDBconnection connection = this._engine.getConnection()) 
        {
            connection.open();

            //implementation of insert data to db
        }
    }
}

well this is my implementation on my controller :

public class HomeController : Controller 
{
    private readonly IProduct _product;

    public HomeController(IProduct product)
    {
        this._product = product;
    }

    public ActionResult index() {

        //this is OK
        var products = this._product.findAll();

        //this is also OK
        var product = this._product.find(Guid.Parse("some_guid"));

        //this is not OK, cause it made the controller depend on concrete class Product
        this._product.create(new Product {
            id = Guid.newGuid(),
            name = "Vader Shirt",
            price = 99.5
        });

        return View();
    }
}

I inject the Product instance to the controller via container with unity. When I call the findAll() and find() method, it was totally fine cause it still let me decouple the controller and the concrete class Product using the IProduct interface. But when I had to do insert operation via create(Product product) method, I had to create an instance of product to do so, hence coupled my controller to a concrete class : Product.

My question is how do I decoupled my controller and at the same time perform the create method from my controller? And I think it goes the same for the update operation.

Answer 1

Stephen Muecke gave a good advice there, try this:

public interface IProductService{
   void CreateProduct(Guid id, string name, double price);
   IEnumerable<Product> FindAll();
   IProduct Find(Guid id);
  }

then your controller:

public class HomeController : Controller 
{
    private readonly IProductService _productService;

    public HomeController(IProductService service)
    {
        this._productService = service;
    }

 public ActionResult index() {

        //this is OK
        var products = this._productService.FindAll();

        //this is also OK
        var product = this._productService.Find(Guid.Parse("some_guid"));

        this._productService.CreateProduct(
            id = Guid.newGuid(),
            name = "Vader Shirt",
            price = 99.5
        );

        return this.View();
    }
}