Dependency Injection C# and ASP.NET with Unity C# with Example

First why we should use depedency injection in our code ? We want to decouple other components from other 
classes in our program. For example we have class AnimalController which have code like this : 
public class AnimalController() 
{ 
private SantaAndHisReindeer _SantaAndHisReindeer = new SantaAndHisReindeer(); 
public AnimalController(){ 
Console.WriteLine(""); 
} 
} 
We look at this code and we think everything is ok but now our AnimalController is reliant on object 
_SantaAndHisReindeer. Automatically my Controller is bad to testing and reusability of my code will be very hard. 
Very good explanation why we should use Depedency Injection and interfaces here. 
If we want Unity to handle DI, the road to achieve this is very simple :) With NuGet( package manager) we can easily 
import unity to our code. 
in Visual Studio Tools -> NuGet Package Manager -> Manage Packages for Solution -> in search input write 
unity -> choose our project-> click install 
Now two files with nice comments will be created. 
in App-Data folder UnityConfig.cs and UnityMvcActivator.cs 
UnityConfig - in RegisterTypes method, we can see type that will be injection in our constructors. 
namespace Vegan.WebUi.App_Start 
{ 
public class UnityConfig 
{ 
#region Unity Container 
private static Lazy container = new Lazy(() => 
{ 
var container = new UnityContainer(); 
RegisterTypes(container); 
return container; 
}); 
/// 
 
/// Gets the configured Unity container. 
/// 
 
public static IUnityContainer GetConfiguredContainer() 
{ 
return container.Value; 
 

} 
#endregion 
/// 
Registers the type mappings with the Unity container.
 
/// The unity container to configure. 
/// There is no need to register concrete types such as controllers or API controllers 
(unless you want to 
/// change the defaults), as Unity allows resolving a concrete type even if it was not previously 
registered. 
public static void RegisterTypes(IUnityContainer container) 
{ 
// NOTE: To load from web.config uncomment the line below. Make sure to add a 
Microsoft.Practices.Unity.Configuration to the using statements. 
//   container.LoadConfiguration(); 
// TODO: Register your types here 
//  container.RegisterType(); 
container.RegisterType(); 
} 
} 
} 
UnityMvcActivator - > also with nice comments which say that this class integrates Unity with ASP.NET 
MVC 
using System.Linq; 
using System.Web.Mvc; 
using Microsoft.Practices.Unity.Mvc; 
[assembly: 
WebActivatorEx.PreApplicationStartMethod(typeof(Vegan.WebUi.App_Start.UnityWebActivator), "Start")] 
[assembly: 
WebActivatorEx.ApplicationShutdownMethod(typeof(Vegan.WebUi.App_Start.UnityWebActivator), 
"Shutdown")] 
namespace Vegan.WebUi.App_Start 
{ 
/// 
Provides the bootstrapping for integrating Unity with ASP.NET MVC.
 
public static class UnityWebActivator 
{ 
/// 
Integrates Unity when the application starts.
 
public static void Start() 
{ 
var container = UnityConfig.GetConfiguredContainer(); 
FilterProviders.Providers.Remove(FilterProviders.Providers.OfType(). 
First()); 
FilterProviders.Providers.Add(new UnityFilterAttributeFilterProvider(container)); 
DependencyResolver.SetResolver(new UnityDependencyResolver(container)); 
// TODO: Uncomment if you want to use PerRequestLifetimeManager 
// 
Microsoft.Web.Infrastructure.DynamicModuleHelper.DynamicModuleUtility.RegisterModule(typeof(UnityPerR 
equestHttpModule)); 
} 
 

/// 
Disposes the Unity container when the application is shut down.
 
public static void Shutdown() 
{ 
var container = UnityConfig.GetConfiguredContainer(); 
container.Dispose(); 
} 
} 
} 
Now we can decouple our Controller from class SantAndHisReindeer :) 
public class AnimalController() 
{ 
private readonly SantaAndHisReindeer _SantaAndHisReindeer; 
public AnimalController(SantaAndHisReindeer SantaAndHisReindeer){ 
_SantAndHisReindeer = SantaAndHisReindeer; 
} 
} 
There is one final thing we must do before running our application. 
In Global.asax.cs we must add new line: UnityWebActivator.Start() which will start, configure Unity and register our 
types. 
using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Web; 
using System.Web.Mvc; 
using System.Web.Optimization; 
using System.Web.Routing; 
using Vegan.WebUi.App_Start; 
namespace Vegan.WebUi 
{ 
public class MvcApplication : System.Web.HttpApplication 
{ 
protected void Application_Start() 
{ 
AreaRegistration.RegisterAllAreas(); 
FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters); 
RouteConfig.RegisterRoutes(RouteTable.Routes); 
BundleConfig.RegisterBundles(BundleTable.Bundles); 
UnityWebActivator.Start(); 
} 
} 
}