Getting started with Ninject

Question

I watched the first 2 beginner tutorials for Ninject on dimecasts.net. Now, I want to use Ninject 2.2 in ASP.NET MVC 3. I want a view with a mocked out Model. I get object reference not set to an instance of an object when calling my service;

    public class HomeController : Controller
    {
        private readonly IMilestoneService _service;

        public HomeController()
        {
        }

        HomeController(IMilestoneService service)
        {
            _service = service;
        }

        public ActionResult Index()
        {
            ViewBag.Message = "Change Request System";

            return View();
        }

        public ActionResult About()
        {
            return View();
        }

        #region Partial views
        public ActionResult Milestone()
        {
            var result = _service.GetMileStones();//OBJECT REF ERROR
            return View(result);
        }
        #endregion
    }

//####GLOBAL.ASAX
//By using the NinjectHttpApplication, it automatically takes care of controllers, starting up mvc, etc.
//Ninject.Web.Mvc
public class MvcApplication : NinjectHttpApplication
{
    public static void RegisterGlobalFilters(GlobalFilterCollection filters)
    {
        filters.Add(new HandleErrorAttribute());
    }

    public static void RegisterRoutes(RouteCollection routes)
    {
        routes.IgnoreRoute("{resource}.axd/{*pathInfo}");

        routes.MapRoute(
            "Default", // Route name
            "{controller}/{action}/{id}", // URL with parameters
            new { controller = "Home", action = "Index", id = UrlParameter.Optional } // Parameter defaults
        );

    }

    protected void Application_Start()
    {
        AreaRegistration.RegisterAllAreas();

        RegisterGlobalFilters(GlobalFilters.Filters);
        RegisterRoutes(RouteTable.Routes);

        //StartNinject();
    }

    #region Inversion of Control

    protected override IKernel CreateKernel()
    {
        return Container;
    }

    static IKernel _container;
    public static IKernel Container
    {
        get
        {
            if (_container == null)
            {
                _container = new StandardKernel(new SiteModule());
            }
            return _container;
        }
    }

    internal class SiteModule : NinjectModule
    {
        public override void Load()
        {
            //Set up ninject bindings here.
            Bind<IMilestoneService>().To<MileStoneService>();
        }
    }
    #endregion
}

I'm using Razor, he's the milestone partial view

@foreach (var item in Model)
{
    <div>item.Name</div>
}

Finally, the Home view Index

@{
    ViewBag.Title = "Home Page";
}

<h2>@ViewBag.Message</h2>
<p>
   @Html.Action("Milestone");
</p>

Edit 11/20/2013

Note that Ninject has since released version 2.0. The changes are nicely outlined on their site. Of Note StandardModule is now NinjectModule and namespace Ninject.Core no longer exists. I was able to replace it with just Ninject.

Answer 1

There is an issue with your controller class, the constructor with the dependency is private. Your controller should look like:

public class HomeController : Controller
{
    private readonly IMilestoneService _service;

    public HomeController(IMilestoneService service)
    {
        _service = service;
    }

}

Don't even include a public parameterless constructor, it isn't even valid, your class needs that dependency to function.

In fact, I also insert a null check against that dependency in the constructor just to be sure my class is valid on construction:

public class HomeController : Controller
{
    private readonly IMilestoneService _service;

    public HomeController(IMilestoneService service)
    {
        _service = service;
        Enforce.NotNull(() => _service); // lambda to auto-magically get variable name for exception
    }

}

There also may be an issue with your MvcApplication class.

Instead of protected void Application_Start(), there is a different function you can override, protected override void OnApplicationStarted()

This is where your calls to setup routing should go:

public class MvcApplication : NinjectHttpApplication
{

    public override void Init()
    {
        base.Init();
        Mappers.Initialize();
    }

    protected override Ninject.IKernel CreateKernel()
    {
        return Ioc.Initialize();
    }

    protected override void OnApplicationStarted()
    {
        AreaRegistration.RegisterAllAreas();
        RegisterRoutes(RouteTable.Routes);
    }

    public static void RegisterRoutes(RouteCollection routes) 
    {
        Routing.RegisterRoutes(routes);
        //RouteDebug.RouteDebugger.RewriteRoutesForTesting(RouteTable.Routes);
    }
}

Of course, if you are already calling Application_Start that's fine too, but I didn't see it in the OP.

Answer 2

Try this in your global.asax file:

//By using the NinjectHttpApplication, it automatically takes care of controllers, starting up ninject, etc.
//Ninject.Web.Mvc
public class MvcApplication : NinjectHttpApplication
{
    //Your other stuff here. No need to call StartNinject().

    #region Inversion of Control

    protected override IKernel CreateKernel()
    {
        return Container;
    }

    static IKernel _container;
    public static IKernel Container
    {
        get
        {
            if (_container == null)
            {
                _container = new StandardKernel(new SiteModule());
            }
            return _container;
        }
    }

    internal class SiteModule : NinjectModule
    {
        public override void Load()
        {
            //Set up ninject bindings here.
            Bind<IMilestoneService>().To<MileStoneService>();
        }
    }
    #endregion
}

Answer 3

I believe if Ninject couldn't bind that interface, you'd get a binding error. This makes me think Ninject is not instantiating your controller.

Have you included Ninject.Web.Mvc?