Question

I m using Ninject 2 and the Ninject.Web.MVC and using the NinjectHttpApplication

Receiving the following error during the logon process: "A single instance of controller MySite.Controllers.AccountController cannot be used to handle multiple requests. If a custom controller factory is in use, make sure that it creates a new instance of the controller for each request."

My global.asax has this:

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


        RegisterAllControllersIn(Assembly.GetExecutingAssembly());
} 
protected override IKernel CreateKernel()
        {
            return new StandardKernel(new MySite.IoCModules.FakeRepositoriesModule(), new MySite.IoCModules.AccountControllerModule());
        }

The AccountControllerModule looks like this:

 public class AccountControllerModule:Module
{
    public override void Load()
    {
        Bind<IFormsAuthentication>().To<FormsAuthenticationService>();
        Bind<IMembershipService>().To<AccountMembershipService>();
        Bind<MembershipProvider>().ToConstant(Membership.Provider);
    }
}

My guess is that it has something to do the lifecycle set during RegisterAllControllersIn...but I m just not sure...any ideas where to go from here?

UPDATE: Just saw it happen to the HomeController too...it s gotta be trying to make a singleton out of it or something right?

Answer 1

The most recent version of Ninject.Web.Mvc is using a transient scope to register the controllers in RegisterAllControllersIn:

public void RegisterAllControllersIn(Assembly assembly, 
                                       Func<Type, string> namingConvention)
{
  foreach (Type type in assembly.GetExportedTypes().Where(IsController))
     _kernel.Bind<IController>()
        .To(type)
        .InTransientScope()
        .Named(namingConvention(type));
}

I looked into the the NinjectControllerFactory class as well. Its CreateController function is pretty basic. It does a TryGet on the kernel for the controller and returns what it gets back -- if it can t find the controller, it delegates to the base class:

public override IController CreateController(RequestContext requestContext, 
                                                    string controllerName)
{
  var controller = Kernel.TryGet<IController>(controllerName.ToLowerInvariant());

  if (controller == null)
    return base.CreateController(requestContext, controllerName);

  var standardController = controller as Controller;

  if (standardController != null)
    standardController.ActionInvoker = new NinjectActionInvoker(Kernel);

  return controller;
}

So, based on the binding setup and based on the factory, it would seem it s not creating objects in Singleton scope. One thing you could do is write a little debug code after you create your kernel and check the bindings yourself to confirm what the scope is. I did a little experiment and added the code to my HttpApplication class show below. Full disclosure, this is using ASP.Net MVC 1.0, so your mileage may vary. If I have the opportunity, I will get the latest MVC 2 preview and try the same experiment.

protected void DumpBindings() {
  var bindings = Kernel.GetBindings(typeof(IController));

  var dummyRequest = new RequestContext(
                           new HttpContextWrapper(HttpContext.Current), 
                           new RouteData());

  foreach (var binding in bindings) {
    var scope = "Custom";
    if (binding.ScopeCallback == StandardScopeCallbacks.Request)
      scope = "Request";
    else if (binding.ScopeCallback == StandardScopeCallbacks.Singleton)
      scope = "Singleton";
    else if (binding.ScopeCallback == StandardScopeCallbacks.Thread)
      scope = "Thread";
    else if (binding.ScopeCallback == StandardScopeCallbacks.Transient)
      scope = "Transient";

    HttpContext.Current.Trace.Write(
      string.Format(
        "Controller: {0} Named: {1} Scope: {2}",
        binding.Service.Name,
        binding.Metadata.Name,
        scope));
    var controllerFactory = ControllerBuilder.Current.GetControllerFactory();

    var controller1 = controllerFactory.CreateController(
                               dummyRequest, binding.Metadata.Name);
    var controller2 = controllerFactory.CreateController(
                               dummyRequest, binding.Metadata.Name);

    HttpContext.Current.Trace.Write(
      string.Format(
        "{0} controller1 == {0} controller2 ? {1}",
        binding.Metadata.Name,
        object.Equals(controller1, controller2)));
  }
}

I called this right after the call to RegisterAllControllersIn in the OnApplicationStarted. It created the following messages in the trace output:

Controller: IController Named: home
Scope: Transient home controller1
== home controller2 ? False Controller: IController Named: account
Scope: Transient account controller1
== account controller2 ? False

So, all this does is confirm that transient scope is being used and that the controller factory is returning a different instance of the same controller when requested. So, the only thing I can think of is that:

Perhaps you are not using the latest builds of Ninject 2 and Ninject.Web.Mvc
The issue is at the MVC level -- i.e. it s reusing the controller created by the factory

Answer 2

Sounds like it s using a singleton, all right. See this page for documentation as to how to control activation behaviors using Ninject.

Note that transient (not singleton) is the default behavior for Ninject.

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