Tuesday, 26 January 2016

Dependency Injection in ASP.NET MVC 4 using Unity IoC Container



As you know, in MVC, Controller depends on Model for data processing or you can say for executing business logic. This article will explain you how can you decouple model layers from the controller layer in an ASP.NET MVC application using Unit DI Container.
Step 1 - Create a new Asp.Net MVC4 Project
First step is to create a new Asp.Net MVC4 Project using Visual Studio 2012 or 2010SP1 as shown below:
  









Step 2 - Install Unity Container
Now install Unity.Mvc4 Container using NuGet Package Manager Console tool as shown below:
You can also do online search for Unity.Mvc4 Container by navigating to Tools=>Extension and Update=>Online options in Visual Studio 2012 or 2010SP1 and install it.
When it will be installed successfully, you will be find the following two references add to your project and a Bootstrapper.cs class file at project level, as shown below:

using System.Web.Mvc;
using Microsoft.Practices.Unity;
using Unity.Mvc4;

namespace MvcNUnit
{
    public static class Bootstrapper
    {
        public static IUnityContainer Initialise()
        {
            var container = BuildUnityContainer();

            DependencyResolver.SetResolver(new UnityDependencyResolver(container));

            return container;
        }

        private static IUnityContainer BuildUnityContainer()
        {
            var container = new UnityContainer();

            // register all your components with the container here
            // it is NOT necessary to register your controllers

            // e.g. container.RegisterType<ITestService, TestService>();

            RegisterTypes(container);

            return container;
        }

        public static void RegisterTypes(IUnityContainer container)
        {

        }
    }
}


Step 3 - Add a New Service Layer
Add a new Folder in the project of the name Repository and add the following interface and a class in this folder:
//Product.cs
public class Product
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Category { get; set; }
    public decimal Price { get; set; }
}

//IProductRepository.cs
public interface IProductRepository
{
    IEnumerable<Product> GetAll();
    Product Get(int id);
    Product Add(Product item);
    bool Update(Product item);
    bool Delete(int id);
}

//ProductRepository.cs
public class ProductRepository : IProductRepository
{
    private List<Product> products = new List<Product>();
    private int _nextId = 1;

    public ProductRepository()
    {
        // Add products for the Demonstration
        Add(new Product { Name = "Computer", Category = "Electronics", Price = 23.54M });
        Add(new Product { Name = "Laptop", Category = "Electronics", Price = 33.75M });
        Add(new Product { Name = "iPhone4", Category = "Phone", Price = 16.99M });
    }

    public IEnumerable GetAll()
    {
        // TO DO : Code to get the list of all the records in database
        return products;

    }

    public Product Get(int id)
    {
        // TO DO : Code to find a record in database
        return products.Find(p => p.Id == id);

    }

    public Product Add(Product item)
    {
        if (item == null)
        {
            throw new ArgumentNullException("item");
        }

        // TO DO : Code to save record into database
        item.Id = _nextId++;
        products.Add(item);

        return item;
    }

    public bool Update(Product item)
    {
        if (item == null)
        {
            throw new ArgumentNullException("item");
        }

        // TO DO : Code to update record into database
        int index = products.FindIndex(p => p.Id == item.Id);
        if (index == -1)
        {
            return false;
        }
        products.RemoveAt(index);
        products.Add(item);

        return true;
    }

    public bool Delete(int id)
    {
        // TO DO : Code to remove the records from database
        products.RemoveAll(p => p.Id == id);

        return true;
    }
}
The above repository acts as a new layer and will be used to decouple the model layer from the controller layer.

Step 4 - Register the Dependency in Bootstrapper.cs file
Replace BuildUnityContainer method's content with the following code that registers the ProductRepository Service. You can also register the Product Controller in which we will inject the dependency, but it is optional.
private static IUnityContainer BuildUnityContainer()
{
    var container = new UnityContainer();

    // register all your components with the container here
    // it is NOT necessary to register your controllers
    container.RegisterType<IProductRepository, ProductRepository>();

    // e.g. container.RegisterType<ITestService, TestService>();
    RegisterTypes(container);

    return container;
}

Step 5 - Inject Service to Controller
Now inject the dependency for the IProductRepository interface using the Product Controller's constructor as shown below:
public class ProductController : Controller
{
    readonly IProductRepository repository;

    //inject dependency
    public ProductController(IProductRepository repository)
    {
        this.repository = repository;
    }

    public ActionResult Index()
    {
        var data = repository.GetAll();
        return View(data);
    }
    //Other Code
}

Step 6 – Setup Dependency Injection with Unity in Global.asax.cs
Now, setup the Bootstrapper class with in the Application_Start method so that it can initialize all dependencies. This will be done by calling Initialise() method of the Bootstrapper class as shown below:
protected void Application_Start()
{
    AreaRegistration.RegisterAllAreas();

    WebApiConfig.Register(GlobalConfiguration.Configuration);
    FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
    RouteConfig.RegisterRoutes(RouteTable.Routes);
    BundleConfig.RegisterBundles(BundleTable.Bundles);
    AuthConfig.RegisterAuth();

    //Setup DI
    Bootstrapper.Initialise();
}

Step 7 - Run the Application and see how it works



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