At the risk of stepping into holy war territory, What are the strengths and weaknesses of these popular DI/IoC frameworks, and could one easily be considered the best? ..:

* Ninject
* Unity 
* Castle.Windsor
* Autofac
* StructureMap 

Are there any other DI/IoC Frameworks for C# that I haven&#39;t listed here?

In context of my use case, I&#39;m building a client WPF app, and a WCF/SQL services infrastructure, ease of use (especially in terms of clear and concise syntax), consistent documentation, good community support and performance are all important factors in my choice.

## Update:

The resources and duplicate questions cited appear to be out of date, can someone with knowledge of all these frameworks come forward and provide some real insight?
 
I realise that most opinion on this subject is likely to be biased, but I am hoping that someone has taken the time to study all these frameworks and have at least a generally objective comparison.

I am quite willing to make my own investigations if this hasn&#39;t been done before, but I assumed this was something at least a few people had done already.

## Second Update:

If you do have experience with more than one DI/IoC container, please rank and summarise the pros and cons of those, thank you. This isn&#39;t an exercise in discovering all the obscure little containers that people have made, I&#39;m looking for comparisons between the popular (and active) frameworks.


How do the major C# DI/IoC frameworks compare?

I&#39;m writing a custom Authorization Filter for asp.net mvc 3. I need to inject a userservice into the class but I have no idea how to do this.

    public class AuthorizeAttribute : FilterAttribute, IAuthorizationFilter
    {
        private IUserService userService;
        private string[] roles;

        public AuthorizeAttribute(params string[] roles)
        {
            this.roles = roles;
        }

        public void OnAuthorization(AuthorizationContext filterContext)
        {
            throw new NotImplementedException();
        }
    }

I&#39;m using ninject for dependency injection. I do not want to use a Factory or service locator pattern.

My bindings look like this in the global.acsx:

        internal class SiteModule : NinjectModule
        {
            public override void Load()
            {
                Bind&lt;IUserService&gt;().To&lt;UserService&gt;();
            }
        }

Dependency Injection with Ninject and Filter attribute for asp.net mvc

I want to get started using Dependency Injection and IOC and I want to get more into using Ninject.

Are there any good application with sourcecode available that is written using Ninject that I can look at as a reference?



Ninject sample application?

This code was generated for me after added entity framework code-first for SQL Server CE using NuGet. They did no changes to any other file. The file `SQLCEEntityFramework.cs` was created and placed in `App_Start` folder.

Does this mean it automatically gets executed or something? The same thing happened when I added Ninject for MVC 3. No code was added to the `global.ascx` file so I have no idea if its plug and play or I have to configure something.

    [assembly: WebActivator.PreApplicationStartMethod(typeof(StackTorrents.WebUI.App_Start.SQLCEEntityFramework), &quot;Start&quot;)]


What does WebActivator do?

Can anyone tell me if i can register an already created instance of a class with Ninject so that it will use this instance everytime it needs injecting?

I suppose you can call it a singleton but I have the instance already created. All the documentation points to creating new instances of a class.

Ninject: Registering an already created instance with Ninject?

We are using ASP.net MVC.

Which of these is the best DI framework Ninject or Unity and why?

Ninject vs Unity for DI

I created a new MVC3 project, hit F5, saw the sample page.

Then I used NuGet to get the [Ninject.MVC extension][1]. I modified my global.asax according to the Ninject documentation, [How To Setup an MVC3 Application][2]: 

    public class MvcApplication : NinjectHttpApplication
    {
       public static void RegisterGlobalFilters(GlobalFilterCollection filters)
       {
           filters.Add(new HandleErrorAttribute());
       }
     
       public static void RegisterRoutes(RouteCollection routes)
       {
           routes.IgnoreRoute(&quot;{resource}.axd/{*pathInfo}&quot;);
     
           routes.MapRoute(
               &quot;Default&quot;, // Route name
               &quot;{controller}/{action}/{id}&quot;, // URL with parameters
               new { controller = &quot;Home&quot;, action = &quot;Index&quot;, 
                   id = UrlParameter.Optional });
       }
     
       protected override IKernel CreateKernel()
       {
           var kernel = new StandardKernel();
           kernel.Load(Assembly.GetExecutingAssembly());
           return kernel;
       }
     
       protected override void OnApplicationStarted()
       {
           base.OnApplicationStarted();
     
           AreaRegistration.RegisterAllAreas();
           RegisterGlobalFilters(GlobalFilters.Filters);
           RegisterRoutes(RouteTable.Routes);
       }
    }

Now when I run the app, I get the yellow screen of death with the following exception:

&gt; InvalidOperationException - Sequence contains no elements.
&gt;
&gt; at System.Linq.Enumerable.Single(...)
&gt; 
&gt; at Ninject.Web.Mvc.Bootstrapper.Initialize(...)
&gt; line 67.

And sure enough, [line 67 of that file][3] calls .Single(), thus throwing the exception.

What am I doing wrong?


  [1]: https://github.com/ninject/ninject.web.mvc
  [2]: https://github.com/ninject/ninject.web.mvc/wiki/Setting-up-an-MVC3-application
  [3]: https://github.com/ninject/ninject.web.mvc/blob/master/mvc3/src/Ninject.Web.Mvc/Bootstrapper.cs#L67





Ninject + MVC3 = InvalidOperationException: Sequence contains no elements

How do I combine constructor injection with &quot;manual&quot; constructor parameters? ie.

    public class SomeObject
    {
        public SomeObject(IService service, float someValue)
        {
        }
    }

Where IService should be resolved/injected by my DI container, and someValue should be specified. How do I mix the two?

Combining DI with constructor parameters?

There are plenty of examples for having it worked on an MVC application. How is it done on Web Forms?

How can I implement Ninject or DI on asp.net Web Forms?

&lt;!-- language-all: lang-cs --&gt;

I have created a new MVC5 project with Web API 2, I then added the Ninject.MVC3 package from NuGet.

Constructor injection is working fine for the MVC5 controllers, but i am getting an error when trying to use it with the Web API Controllers.

&gt; An error occurred when trying to create a controller of type &#39;UserProfileController&#39;. Make sure that the controller has a parameterless public constructor.

Constructor for working MVC5 controller:

    public class HomeController : Controller
    {
        private IMailService _mail;
        private IRepository _repo;

        public HomeController(IMailService mail, IRepository repo)
        {
            _mail = mail;
            _repo = repo;
        }
    }


Constructor for non-working Web API Controller:

    public class UserProfileController : ApiController
    {
        private IRepository _repo;

        public UserProfileController(IRepository repo)
        {
            _repo = repo;
        }
    }

Below is the full NinjectWebCommon.cs file:


    [assembly: WebActivator.PreApplicationStartMethod(typeof(DatingSite.App_Start.NinjectWebCommon), &quot;Start&quot;)]
    [assembly: WebActivator.ApplicationShutdownMethodAttribute(typeof(DatingSite.App_Start.NinjectWebCommon), &quot;Stop&quot;)]

    namespace DatingSite.App_Start
    {
    using System;
    using System.Web;

    using Microsoft.Web.Infrastructure.DynamicModuleHelper;

    using Ninject;
    using Ninject.Web.Common;
    using DatingSite.Services;
    using DatingSite.Data;

    public static class NinjectWebCommon
    {
        private static readonly Bootstrapper bootstrapper = new Bootstrapper();

        /// &lt;summary&gt;
        /// Starts the application
        /// &lt;/summary&gt;
        public static void Start()
        {
            DynamicModuleUtility.RegisterModule(typeof(OnePerRequestHttpModule));
            DynamicModuleUtility.RegisterModule(typeof(NinjectHttpModule));
            bootstrapper.Initialize(CreateKernel);
        }

        /// &lt;summary&gt;
        /// Stops the application.
        /// &lt;/summary&gt;
        public static void Stop()
        {
            bootstrapper.ShutDown();
        }

        /// &lt;summary&gt;
        /// Creates the kernel that will manage your application.
        /// &lt;/summary&gt;
        /// &lt;returns&gt;The created kernel.&lt;/returns&gt;
        private static IKernel CreateKernel()
        {
            var kernel = new StandardKernel();
            kernel.Bind&lt;Func&lt;IKernel&gt;&gt;().ToMethod(ctx =&gt; () =&gt; new Bootstrapper().Kernel);
            kernel.Bind&lt;IHttpModule&gt;().To&lt;HttpApplicationInitializationHttpModule&gt;();

            RegisterServices(kernel);
            return kernel;
        }

        /// &lt;summary&gt;
        /// Load your modules or register your services here!
        /// &lt;/summary&gt;
        /// &lt;param name=&quot;kernel&quot;&gt;The kernel.&lt;/param&gt;
        private static void RegisterServices(IKernel kernel)
        {
    #if DEBUG
            kernel.Bind&lt;IMailService&gt;().To&lt;MockMailService&gt;().InRequestScope();

    #else
            kernel.Bind&lt;IMailService&gt;().To&lt;MailService&gt;().InRequestScope();
    #endif
            kernel.Bind&lt;SiteContext&gt;().To&lt;SiteContext&gt;().InRequestScope();
            kernel.Bind&lt;IRepository&gt;().To&lt;Repository&gt;().InRequestScope();
        }
    }
    }



MVC5, Web API 2 and Ninject

Using EF5 with a generic Repository Pattern and ninject for dependency injenction and running into an issue when trying to update an entity to the database utilizing stored procs with my edmx.  

my update in DbContextRepository.cs is:

    public override void Update(T entity)
    {
        if (entity == null)
            throw new ArgumentException(&quot;Cannot add a null entity.&quot;);

        var entry = _context.Entry&lt;T&gt;(entity);

        if (entry.State == EntityState.Detached)
        {
            _context.Set&lt;T&gt;().Attach(entity);
            entry.State = EntityState.Modified;
        }
    }


From my AddressService.cs which goes back to my repository I have:

     public int Save(vw_address address)
    {
        if (address.address_pk == 0)
        {
            _repo.Insert(address);
        }
        else
        {
            _repo.Update(address);
        }

        _repo.SaveChanges();

        return address.address_pk;
    }

When it hits the Attach and EntityState.Modified it pukes with the error:

**An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key.**

I have looked through many of the suggestions in stack and on the Internet and not coming up with anything that resolves it.  Any work arounds would be appreciated.

Thanks!

An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key

It&#39;s a Web API 2 project.

When I implement DI using Ninject, I got an error message

An error occurred when trying to create a controller of type &#39;TokenController&#39;. Make sure that the controller has a parameterless public constructor.

    [assembly: OwinStartup(typeof(Web.Startup))]

    namespace Web
    {
        public partial class Startup
        {
            public void Configuration(IAppBuilder app)
            {
                ConfigureAuth(app);
                ConfigureWebApi(app);
            }
        }
    }

    public class TokenController : ApiController
    {

        private IUserService _userService;

        public TokenController(IUserService userService)
        {
            this._userService = userService;
        }

        [Route(&quot;api/Token&quot;)]
        public HttpResponseMessage PostToken(UserViewModel model)
        {
            if (_userService.ValidateUser(model.Account, model.Password))
            {
                ClaimsIdentity identity = new ClaimsIdentity(Startup.OAuthBearerOptions.AuthenticationType);
                identity.AddClaim(new Claim(ClaimTypes.Name, model.Account));
                AuthenticationTicket ticket = new AuthenticationTicket(identity, new AuthenticationProperties());
                var currentUtc = new SystemClock().UtcNow;
                ticket.Properties.IssuedUtc = currentUtc;
                ticket.Properties.ExpiresUtc = currentUtc.Add(TimeSpan.FromMinutes(30));
                return new HttpResponseMessage(HttpStatusCode.OK)
                {
                    Content = new ObjectContent&lt;object&gt;(new
                    {
                        UserName = model.Account,
                        AccessToken = Startup.OAuthBearerOptions.AccessTokenFormat.Protect(ticket)
                    }, Configuration.Formatters.JsonFormatter)
                };
            }

            return new HttpResponseMessage(HttpStatusCode.BadRequest);
        }
    }

When I add `&lt;add key=&quot;owin:AutomaticAppStartup&quot; value=&quot;false&quot; /&gt;` to web.config

Ninject works fine, 
but **Startup.OAuthBearerOptions.AccessTokenFormat** becomes to null

How to use DI container with OWIN?

**UPDATE**

Implement IDependencyResolver and use the WebAPI Dependency Resolver as below

    public void ConfigureWebApi(IAppBuilder app)
    {
        HttpConfiguration config = new HttpConfiguration();

        config.DependencyResolver = new NinjectDependencyResolver(NinjectWebCommon.CreateKernel());

        app.UseWebApi(config);
    }

[NinjectDependencyResolver](http://www.peterprovost.org/blog/2012/06/19/adding-ninject-to-web-api)

---

In Simple Injector case

    public void ConfigureWebApi(IAppBuilder app)
    {
        HttpConfiguration config = new HttpConfiguration();

        var container = new Container();
        container.Register&lt;IUserService, UserService&gt;();
        config.DependencyResolver = new SimpleInjectorWebApiDependencyResolver(container);

        app.UseWebApi(config);
    }

[SimpleInjectorWebApiDependencyResolver](http://simpleinjector.codeplex.com/wikipage?title=Web%20API%20Integration)

How to use DI container when OwinStartup

My question is a bit related to this: https://stackoverflow.com/questions/23395632/webapi-equivalent-for-httpcontext-items-with-dependency-injection. 

*We want to inject a class using HttpContext.Current in WebApi area using Ninject.*

My concern is, this could be **very dangerous**, as in WebApi (*everything?*) is async.

Please correct me if I am wrong in these points, this is what I investigated so far:

1. HttpContext.Current gets the current context by Thread (I looked into the implementation directly).

2. Using HttpContext.Current inside of async Task is not possible, because it can run on another Thread.

3. WebApi uses IHttpController with method `Task&lt;HttpResponseMessage&gt; ExecuteAsync` =&gt; every request is async =&gt; you cannot use HttpContext.Current inside of action method. It could even happen, more Request are executed on the same thread by coicidence.

4. For creating controllers with injected stuff into constructors `IHttpControllerActivator` is used with **sync** method `IHttpController Create`. This is, where ninject creates Controller with all its dependencies.

---

- If I am correct in all of these 4 points, using of `HttpContext.Current` inside of an action method or any layer below is very dangerous and can have unexpected results. I saw on StackOverflow lot of accepted answers suggesting exactly this. In my opinion this can work for a while, but will fail under load.

- But when using DI to create a Controller and its dependencies, it is Ok, because this runs on one separated thread. **I could get a value from the HttpContext in the constructor and it would be safe?**. I wonder if each Controller is created on single thread for every request, as this could cause problem under heavy loads, where all threads from IIS could be consumed.

*Just to explain why I want to inject HttpContext stuff:*

  - one solution would be to get the request in controller action method and pass the needed value all the layers as param until its used somewhere deep in the code.
  - our wanted solution: all the layers between are not affected by this, and we can use the injected request somewhere deep in code (e.g. in some `ConfigurationProvider` which is dependent on URL)
  
  
 Please give me your opinion if I am totally wrong or my suggestions are correct, as this theme seems to be very complicated.

Using HttpContext.Current in WebApi is dangerous because of async

I decided to start using Ninject and face an issue. Say I have the following scenario.
I have an `IService` interface and 2 classes implementing this interface. And also I have a class, which has a constructor getting IService and an __int__. How can I create an instance of this class with Ninject (I dont want to hardwire this int, I want to pass it every time I get an instance)?

Here&#39;s some code illustrating the situation:

    interface IService
    {
        void Func();
    }

    class StandardService : IService
    {
        public void Func()
        {
            Console.WriteLine(&quot;Standard&quot;);
        }
    }

    class AlternativeService : IService
    {
        public void Func()
        {
            Console.WriteLine(&quot;Alternative&quot;);
        }
    }


    class MyClass
    {
        public MyClass(IService service, int i)
        {
            this.service = service;
        }

        public void Func()
        {
            service.Func();
        }

        IService service = null;
    }
    class Program
    {
        static void Main(string[] args)
        {
            IKernel kernel = new StandardKernel(new InlineModule(
                x =&gt; x.Bind&lt;IService&gt;().To&lt;AlternativeService&gt;(),
                x =&gt; x.Bind&lt;MyClass&gt;().ToSelf()));

            IService service = kernel.Get&lt;IService&gt;();

            MyClass m = kernel.Get&lt;MyClass&gt;();
            m.Func();
        }
    }

Creating an instance using Ninject with additional parameters in the constructor

I&#39;m a complete newbie to ninject

I&#39;ve been pulling apart someone else&#39;s code and found several instances of nInject modules - classes that derive from Ninject.Modules.Module, and have a load method that contains most of their code.

These classes are called by invoking the LoadModule method of an instance of StandardKernel and passing it an instance of the module class.

Maybe I&#39;m missing something obvious here, but what is the benefit of this over just creating a plain old class and calling its method, or perhaps a static class with a static method?


&amp;nbsp;

What is the intention of Ninject modules?

I have been helping a few friends on a project and there is a class that uses Ninject. I am fairly new to C# and I have no idea what that class is doing, which is why I need to understand Ninject. Can anyone explain what Ninject is and when does one use it(with example if possible)? Or if you can point to some links that would be great too.

I tried this question: &lt;https://stackoverflow.com/questions/5239061/ninject-tutorials-documentations&gt; but it didn&#39;t really help a beginner like me. 

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