Getting Ninject to work

Question

Clearly, I am missing something. I have an MVC application and have installed Ninject 3 and the MVC3 extensions (although I am running MVC4). I have a SiteSettings class that is referenced throughout the project, which looks like this:

public class SiteSettings
{
    private static readonly Common.Logging.ILog Logger = Common.Logging.LogManager.GetCurrentClassLogger();
    private static ObservableDictionary<string, string> settings;
    private static bool Initialized = false;
    private static DataPersister persister;

    public static void Initialize()
    {
        if (Initialized) throw new InvalidOperationException("The SiteSettings object has already been initialized.");
        persister = new DataPersister();
        using (var u = persister.UnitOfWorkFactory.GetUnitOfWork())
        {
            var settingsList = u.SiteSettings.GetAll();
            settings = new ObservableDictionary<string, string>(settingsList.ToDictionary(key => key.SiteSettingName, value => value.SiteSettingValue));
            settings.OnChange += new kvpChangeEvent<string, string>(settings_OnChange);
        }
        Initialized = true;
    }

    static void settings_OnChange(object sender, odKVPChangeEventArgs<string, string> e)
    {
        using (var u = persister.UnitOfWorkFactory.GetUnitOfWork())
        {
            var setting = u.SiteSettings.GetByName(e.Key);
            setting.SiteSettingValue = e.Value;
            u.SiteSettings.Update(setting);
            u.Save();
            Logger.Info(i => i("Changed the '{0}' site setting from '{1}' to '{2}'.", e.Key, e.OldValue, e.Value));
        }
    }

    private static int _ItemsPerPage;
    public static int ItemsPerPage
    {
        get
        {
            return _ItemsPerPage;
        }
        set
        {
            _ItemsPerPage = value;
            settings["itemsPerPage"] = value.ToString();
        }
    }

    private static int _SessionLifeInMinutes;
    public static int SessionLifeInMinutes
    {
        get
        {
            return _SessionLifeInMinutes;
        }
        set
        {
            _SessionLifeInMinutes = value;
            settings["sessionLifeInMinutes"] = value.ToString();
        }
    }

    private static string _DateFormat;
    public static string DateFormat
    {
        get
        {
            return _DateFormat;
        }
        set
        {
            _DateFormat = value;
            settings["defaultDateFormat"] = value;
        }
    }
}

I built a data persistence object like so:

public class DataPersister
{
    public IUnitOfWorkFactory UnitOfWorkFactory { get; set; }
}

... and I have my NinjectWebCommon.cs looks like this:

public static class NinjectWebCommon
{
    private static readonly Bootstrapper bootstrapper = new Bootstrapper();

    /// <summary>
    /// Starts the application
    /// </summary>
    public static void Start()
    {
        DynamicModuleUtility.RegisterModule(typeof(OnePerRequestHttpModule));
        DynamicModuleUtility.RegisterModule(typeof(NinjectHttpModule));
        bootstrapper.Initialize(CreateKernel);
    }

    /// <summary>
    /// Stops the application.
    /// </summary>
    public static void Stop()
    {
        bootstrapper.ShutDown();
    }

    /// <summary>
    /// Creates the kernel that will manage your application.
    /// </summary>
    /// <returns>The created kernel.</returns>
    private static IKernel CreateKernel()
    {
        var kernel = new StandardKernel();
        kernel.Bind<Func<IKernel>>().ToMethod(ctx => () => new Bootstrapper().Kernel);
        kernel.Bind<IHttpModule>().To<HttpApplicationInitializationHttpModule>();

        RegisterServices(kernel);
        return kernel;
    }

    /// <summary>
    /// Load your modules or register your services here!
    /// </summary>
    /// <param name="kernel">The kernel.</param>
    private static void RegisterServices(IKernel kernel)
    {
        kernel.Bind<IUnitOfWork>().To<NHUnitOfWork>();
        kernel.Bind<IUnitOfWorkFactory>().To<NHUnitOfWorkFactory>();
    }
}

It seems to me I've met all my requirements for dependency injection. My Global.asax.cs Application_Start() looks like this:

protected void Application_Start()
{
    ViewEngines.Engines.Clear();
    ViewEngines.Engines.Add(new MonoRazorViewEngine());

    AreaRegistration.RegisterAllAreas();
    RegisterGlobalFilters(GlobalFilters.Filters);
    RegisterRoutes(RouteTable.Routes);
    ControllerBuilder.Current.DefaultNamespaces.Add("MyApplication.Application.Controllers");
    Initialize.Security();
    SiteSettings.Initialize();
}

...and yet, my SiteSettings class always has a null IUnitOfWorkFactory when I try to collect the data I need.

What am I doing wrong? Everything seems to be as all the examples suggest it should be, but I get no love.

UPDATE

Using Bassam Mehanni's advice, I rewrote my DataPersister class to look like this:

public class DataPersister
{
    private IUnitOfWorkFactory UnitOfWorkFactory;
    public DataPersister(IUnitOfWorkFactory unitOfWorkFactory)
    {
        UnitOfWorkFactory = unitOfWorkFactory;
    }
    public IUnitOfWork GetUnitOfWork()
    {
        return UnitOfWorkFactory.GetUnitOfWork();
    }
}

...but of course now my SiteSettings class complains about my parameterless constructor. What should I do about that?

UPDATE 2

Ok, continuing on, I rewrote my DataPersister class like so:

public class DataPersister
{
    private static readonly Common.Logging.ILog Logger = Common.Logging.LogManager.GetCurrentClassLogger();

    private IUnitOfWorkFactory UnitOfWorkFactory { get; set; }
    public IUnitOfWork GetUnitOfWork()
    {
        return UnitOfWorkFactory.GetUnitOfWork();
    }
    [Inject]
    public DataPersister(IUnitOfWorkFactory factory)
    {
        Logger.Info("Injected constructor called");
        UnitOfWorkFactory = factory;
    }
    public DataPersister()
    {
        Logger.Info("Parameterless constructor called");
    }
}

then I rewrote my SiteSettings class like so:

public class SiteSettings
{
    private static readonly Common.Logging.ILog Logger = Common.Logging.LogManager.GetCurrentClassLogger();
    private ObservableDictionary<string, string> settings;
    private DataPersister persister;
    private SiteSettings()
    {
        persister = new DataPersister();
        using (var u = persister.GetUnitOfWork())
        {
            var settingsList = u.SiteSettings.GetAll();
            settings = new ObservableDictionary<string, string>(settingsList.ToDictionary(key => key.SiteSettingName, value => value.SiteSettingValue));
            settings.OnChange += new kvpChangeEvent<string, string>(settings_OnChange);
        }
    }
    private static SiteSettings instance;

    public static SiteSettings Instance
    {
        get
        {
            if (instance == null)
            {
                instance = new SiteSettings();
            }
            return instance;
        }
    }

    private void settings_OnChange(object sender, odKVPChangeEventArgs<string, string> e)
    {
        using (var u = persister.GetUnitOfWork())
        {
            var setting = u.SiteSettings.GetByName(e.Key);
            setting.SiteSettingValue = e.Value;
            u.SiteSettings.Update(setting);
            u.Save();
            Logger.Info(i => i("Changed the '{0}' site setting from '{1}' to '{2}'.", e.Key, e.OldValue, e.Value));
        }
    }

    private int _ItemsPerPage;
    public int ItemsPerPage
    {
        get
        {
            return _ItemsPerPage;
        }
        set
        {
            _ItemsPerPage = value;
            settings["itemsPerPage"] = value.ToString();
        }
    }

    private int _SessionLifeInMinutes;
    public int SessionLifeInMinutes
    {
        get
        {
            return _SessionLifeInMinutes;
        }
        set
        {
            _SessionLifeInMinutes = value;
            settings["sessionLifeInMinutes"] = value.ToString();
        }
    }

    private string _DateFormat;
    public string DateFormat
    {
        get
        {
            return _DateFormat;
        }
        set
        {
            _DateFormat = value;
            settings["defaultDateFormat"] = value;
        }
    }
}

Shouldn't this work? because it doesn't. The DataPersister class always gets called with the parameterless constructor. My kernel binding looks like this:

private static void RegisterServices(IKernel kernel)
{
    kernel.Bind<IUnitOfWork>().To<NHUnitOfWork>();
    kernel.Bind<IUnitOfWorkFactory>().To<NHUnitOfWorkFactory>();
}

Is there something else I am missing? This is getting very frustrating.

Answer 1

Static classes that depencend on none static classes is something you shouldn't do when using an IoC container. Instead you should create a none static class with a singleton lifetime.

1. Make your SiteSettings class none static.
2. Inject all dependencies e.g. IUnitOfWorkFactory into SiteSettings using constructor injection
3. Create a binding in singleton scope for SiteSettings
4. Get an instance of SiteSettings wherever you need access unsing constructor injection.

Example:

public class SiteSettings {
    public SiteSettings(IUnitOfWorkFactory uowFactory) { .... }

    ....
}


public class INeedToAccessSiteSettings
{
    public INeedToAccessSiteSettings(SiteSettings siteSettings) { .... }
}

kenrel.Bind<SiteSettings>().ToSelf().InSingletonScope();

Answer 2

Typically ninject will inject your service in a constructor or something, it doesn't magically turn all your interfaces to object instances at run time

e.g.:

public class MyController : Controller
{
   private IServiceThatINeed _serviceThatINeed;
   public MyController(IServiceThatINeed serviceThatINeed)
   { 
       _serviceThatINeed = _serviceThatINeed;
   }
}

in this case since you registered your kernel instance, mvc knows how to resolve this dependence and will pass an instance of an object that implement IServiceThatINeed (assuming that you told ninject how to resolve this dependency.

Now there might be instance where you will need to get a service without it being injected in a constructor by the mvc framework, in these instances (like the one you have here), you will need to use ServiceLocator

e.g.:

var myService = ServiceLocator.Current.GetInstance<IServiceThatINeed>()

to use the ServiceLocator, you need to add a reference to Microsoft.Practices.ServiceLocation

Hope that helps!