Saturday, May 26, 2018

Part 56 - Repository Pattern - 3 - Dependency Injection using Microsoft Unity


In this tutorial, You will learn about how to implement Dependency Injection in  Asp.net MVC using Microsoft Unity plugin.  In previous tutorial we learned about how to add Business Layer  and Domain Layer. Lets look at below layers and get little idea about what is the use of them.

1. Web Layer is your MVC web Project
2. Business Layer consist the CRUD operation, gets data from Data Access Layer, Manipulate them and finally returns data to the Controller ( Web Layer)
3. Domain Layer consist the Domain Models or Classes that hold the data coming from Data Access Layer. Both Web and Business Layer can use domain models to exchange data.
4. Data Access Layer consist the generic repository methods (generic CRUD operation), Unit of Work( Database Context) and NON Generic repository( User defined repository).


# What is Dependency Injection? 
Dependency Injection is a software design pattern that help us to develop loosely coupled code. 
Loose coupling offers below advantages 

  1. Increases code “Reusability”
  2. Improves code “Maintainability”
  3. Improves “Testability”

Real life Example: In above picture, the boy and girl are married, it means they are highly dependent on each other or you can say they are tightly coupled. But after using dependency injection they become loosely coupled or independent. In real life, getting divorced is not a good solution . On the contrary, in Software architecture it would be one of the best solution. 

 We might have seen in a big project , several sets of developer working on different modules . It would be a great idea if they can work independently without effecting other's work. 

 Generally, we have dependency on object of a class that creates a tightly coupled architecture.
For example, we have a class in our Business Layer and it consist some methods. Now if I create the instance of this class into my Web Layer's controller then, both Business and Web Layer will be tightly coupled. 

 Our basic idea of using dependency injection is to remove dependency from our persistence resource like entity framework.  

 # What are the ways to implement Dependency Injection?
 we can use any of the following way

  1. Constructor Injection
  2. Property/Setter injection
  3. Method injection



 In this tutorial, we will be implementing DI using Constructor Injection. In this, we pass the dependent object as a parameter into the constructor  of the controller


# Steps to implement Dependency Injection using Microsoft Unity?

Step 1 :  Right Click on your solution and click on Manage NuGet Package



 Step 2 :  Search Unity.MVC5 and install the plugin



Step 3 : After installing plugin, a config file(UnityConfig.cs) will be created in your AppConfig Folder. Open that file and add below setting into this.


 Copy "container.RegisterType<IEmployeeBusiness, EmployeeBusiness>();"  in your UnityConfig.cs file. I expecting, you already have watched my previous tutorial i.e How to add Business Layer  and Domain Layer in MVC. Copy


using MVCTutorial.Business;
using MVCTutorial.Business.Interface;
using MVCTutorial.Infrastructure;
using System.Web.Mvc;
using Unity;
using Unity.Injection;
using Unity.Mvc5;

namespace MVCTutorial
{
    public static class UnityConfig
    {
        public static void RegisterComponents()
        {
   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>();

            container.RegisterType<IEmployeeBusiness, EmployeeBusiness>();
           
            DependencyResolver.SetResolver(new UnityDependencyResolver(container));
        }
    }
}


Step 4 :(IGNORE this step if you already have below interface and Class created in your project). 
In previous tutorial(How to add Business Layer) if you do remember, we added interface and concrete class into our Business Layer. Do you? If not then create  Business Layer and do below things..
 "Add an Interface Folder into your business layer then create IEmployeBusiness interface and finally add a method into this example: GetEmployeeName(). After adding interface, add a concrete class EmpolyeeBusiness which will implement the IEmployeeBusiness Methods. Please see below screenshot. Copy below code in your interface and class."  


A. IEmployeeBusiness( Interface) 
using MVCTutorial.Domain;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace MVCTutorial.Business.Interface
{
    public interface IEmployeeBusiness
    {
        string GetEmployeeName(int EmpId);
        List<EmployeeDomainModel> GetAllEmployee();
    }
}

B. Employeebusiness ( Concrete class)

using MVCTutorial.Business.Interface;
using MVCTutorial.Domain;
using MVCTutorial.Repository;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace MVCTutorial.Business
{
    public class EmployeeBusiness : IEmployeeBusiness
    {

        public string GetEmployeeName(int EmpId)
        {
            return "Ashish" + EmpId;
        }

        public List<EmployeeDomainModel> GetAllEmployee()
        {
            List<EmployeeDomainModel> list = new List<EmployeeDomainModel>();

            list.Add(new EmployeeDomainModel { Name = "Ashish", EmployeeId = 1 });
            list.Add(new EmployeeDomainModel { Name = "Rob", EmployeeId = 2 });
            list.Add(new EmployeeDomainModel { Name = "Sara", EmployeeId = 3 });
            list.Add(new EmployeeDomainModel { Name = "Jack", EmployeeId = 4 });
            list.Add(new EmployeeDomainModel { Name = "Peter", EmployeeId = 5 });

            return list;

        }
    }
}



Step 5 :  Open your RepoController.cs file and paste below code. Here you can see, I have passed an interface object(IEmployeeBusiness empBusiness) as a parameter into the constructor of the controller. But wait, instead of interface I was expecting to pass the instance of EmployeeBusiness. If I directly pass it into the constructor then it will not follow the OOP Principle - "depend on the abstraction not on the concrete classes".  So in this situation, Unity5 plugin help me to resolve this problem automatically.

#Controller Code(RepoController.cs) : 

using MVCTutorial.Business;
using MVCTutorial.Business.Interface;
using MVCTutorial.Domain;
using MVCTutorial.Models;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;

namespace MVCTutorial.Controllers
{
    public class RepoController : Controller
    {
        IEmployeeBusiness _empBusiness;

        // oop principle: depend on the abstraction not on the concrete classes

        public RepoController(IEmployeeBusiness empBusiness)
        {
            _empBusiness = empBusiness;
        }

        // GET: Repo
        public ActionResult Index()
        {

            ViewBag.EmpName = _empBusiness.GetEmployeeName(254);

            List<EmployeeDomainModel> listDomain = _empBusiness.GetAllEmployee();

            List<EmployeeViewModel> listemployeeVM = new List<EmployeeViewModel>();

            AutoMapper.Mapper.Map(listDomain, listemployeeVM);

            ViewBag.EmployeeList = listemployeeVM;


            return View();
        }
    }
}

Step 6 :  Go to your Global.asax file and add "UnityConfig.RegisterComponents();" into this. 


using MVCTutorial.Infrastructure;
using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Threading;
using System.Web;
using System.Web.Mvc;
using System.Web.Optimization;
using System.Web.Routing;

namespace MVCTutorial
{
    public class MvcApplication : System.Web.HttpApplication
    {
        protected void Application_Start()
        {
            AreaRegistration.RegisterAllAreas();
            UnityConfig.RegisterComponents();
            FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
            RouteConfig.RegisterRoutes(RouteTable.Routes);
            BundleConfig.RegisterBundles(BundleTable.Bundles);
            AutomapperWebProfile.Run();

            //System.Web.Optimization.BundleTable.EnableOptimizations = true;
        }

       
    }
}

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