I'm using SignalR 0.5.2 and I'm trying to get a DependencyResolver set up using Unity. I've written the simplest code I can. I have a hub that I'm trying to inject into which looks like this:
public class SimpleHub : Hub
{
private readonly ITestService _service;
public SimpleHub(ITestService service)
{
_service = service;
}
public void Update()
{
Clients.callback("Kevin");
}
}
and a DependencyResolver that looks like this:
public class UnityDependencyResolver : DefaultDependencyResolver
{
private readonly IUnityContainer _container;
public UnityDependencyResolver(IUnityContainer container)
{
_container = container;
}
public override object GetService(Type serviceType)
{
if (_container.IsRegistered(serviceType))
{
return _container.Resolve(serviceType);
}
return base.GetService(serviceType);
}
public override IEnumerable<object> GetServices(Type serviceType)
{
if (_container.IsRegistered(serviceType))
{
return _container.ResolveAll(serviceType);
}
return base.GetServices(serviceType);
}
}
I register the dependency resolver in Global.asax
protected void Application_Start()
{
IUnityContainer container = new UnityContainer();
InitializeContainer(container);
SignalR.IDependencyResolver resolver = new UnityDependencyResolver(container);
GlobalHost.DependencyResolver = resolver;
RouteTable.Routes.MapHubs();
// more MVC stuff here
}
where InitializeContainer register the ITestService in Unity
The resolver "works" in that it's getting called for all the SignalR types, and if I leave my hub with a default constructor it all gets loaded. However the resolver never gets asked to resolve the ITestService interface.
I've also tried passing the resolver to MapHubs, still no luck. I've also tried property injection using the [Dependency] attribute and that didn't work either.
Do I need to register the resolver with MVC as well? (I have tried that by implementing both IDependecyResolver interfaces but get an exception telling me the resolver doesn't implement IServiceLocator)
So I've sort of fixed this. I wondered if the fact that the Hub was registered with the signalr container and the interface was registered with the Unity container was causing the issue. So I registered the Hub with Unity and then everything works.
This sort of makes sense as there are two containers.
Is this the standard behaviour?
In case someone else is wondering... I found a good SPA example that uses
SignalR 1.0.1
Unity 3
A bunch of other frameworks
The interesting thing is the way he create the container, the dependencies and everything else. Worth checking it out.
Related
Trying to wrap my head around dependency injection, coming from the world of static classes and instantiated classes. Here is what I currently have:
[SomeFilter]
public class AController : Controller
{
private readonly IOptions<AppSettings> _appSettings;
public AController(IOptions<AppSettings> appSettings)
{
_appSettings = appSettings;
}
// GET: /characters/
public IActionResult Index()
{
//do something
}
SomeFilter gets called immediately, and does this:
public class SomeFilter: ActionFilterAttribute, IActionFilter
{
public override void OnActionExecuting(ActionExecutingContext filterContext)
{
OtherClass.RunMe();
}
}
OtherClass looks like this:
public class OtherClass
{
private readonly IOptions<AppSettings> _appSettings;
public OtherClass(IOptions<AppSettings> appSettings)
{
_appSettings = appSettings;
}
public RunMe()
{
//do something
}
I also have OtherClass registered as a service.Singleton in the Startup.cs.
I get an error stating:
"An object reference is required for a non-static field"
for the OtherClass.RunMe(); call.
I was under the assumption that I can call this class from anywhere within my code instead of having to create a new instance of it? Essentially, how do I call methods from other classes using dependency injection?
You can't constructor injection on filters. It's all about run time order. When you try injection on constructor, your IoC container not reachable at the moment. You should be use property/setter injection.
I prefer using structuremap container for to do this. Because structuremap has very easy to apply any type injection. For example when you have a filter registry like this
public class ActionFilterRegistry : Registry
{
public ActionFilterRegistry(Func<IContainer> containerFactory)
{
For<IFilterProvider>().Use(
new StructureMapFilterProvider(containerFactory));
Policies.SetAllProperties(x =>
x.Matching(p =>
p.DeclaringType.CanBeCastTo(typeof(ActionFilterAttribute)) &&
p.DeclaringType.Namespace.StartsWith("YourNameSpace") &&
!p.PropertyType.IsPrimitive &&
p.PropertyType != typeof(string)));
}
}
And you register it on your global.asax(prefer) or one of your startup class.
Example app_Start method.
DependencyResolver.SetResolver(new StructureMapDependencyResolver(() => Container ?? ObjectFactory.Container));
ObjectFactory.Container.Configure(cfg =>
{
cfg.AddRegistry(new StandardRegistry());
cfg.AddRegistry(new ControllerRegistry());
cfg.AddRegistry(new ActionFilterRegistry(() => Container));
cfg.AddRegistry(new MvcRegistry());
});
Then you can use any filter with injection. But pay attention you shouldn't be use contructor injection like you do.
I found a way to inject into the filter by using
[ServiceFilter(typeof(MyFilter))]
instead of just
[MyFilter]
and within the filter's
(ActionExecutingContext context)
{
var controller = context.Controller as Controller.
controller.whateverIneed
}
This now provides me with what I need within the filter. What I also realized is that I can't remove the need for creating references to other classes using new, as I was under the impression Core's dependency was all about "no more new". This gets into fundamentals with Core which I'm still grasping with.
What I ended up doing was creating new classes that do some work, but they are setup as services and registered in the startup.cs. I'm still grappling on how to intermingle registered services (which I can inject) and new instances of worker classes (which usually hold static information), and passing information between them all.
I'm developing an ASP.NET MVC 5 Web API application with C#, .NET Framework 4.5.1, Entity Framework 6.1.1 and the latest version of Ninject (I have also installed Ninject.MVC5).
I'm learning how to implement dependency injection, and I think I have learned it, but I have a question. These are my interfaces and classes.
Unit of work interface:
public interface IUnitOfWork
{
void Commit();
}
Custom DbContext implementation (I use IUnitOfWork interface to allow DI):
public class EFDbContext : DbContext, IUnitOfWork
{
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
[ ... ]
}
public void Commit()
{
this.SaveChanges();
}
}
And this is how allow Dependency Injection with Ninject and Ninject.Web.Common.
I have a class, NinjectConfigurator, that adds bindings:
public class NinjectConfigurator
{
public void Configure(IKernel container)
{
// Add all bindings/dependencies
AddBindings(container);
// Use the container and our NinjectDependencyResolver as
// application's resolver
var resolver = new NinjectDependencyResolver(container);
GlobalConfiguration.Configuration.DependencyResolver = resolver;
}
private void AddBindings(IKernel container)
{
ConfigureLog4net(container);
container.Bind<IUnitOfWork>().To<EFDbContext>().InRequestScope();
container.Bind<IGenericRepository<User>>().To<GenericRepository<User>>();
}
private void ConfigureLog4net(IKernel container)
{
log4net.Config.XmlConfigurator.Configure();
var loggerForWebSite = LogManager.GetLogger("MattSocialNetworkWebApi");
container.Bind<ILog>().ToConstant(loggerForWebSite);
}
}
And finally, I have this on NinjectWebCommon:
/// <summary>
/// Load your modules or register your services here!
/// </summary>
/// <param name="kernel">The kernel.</param>
private static void RegisterServices(IKernel kernel)
{
var containerConfigurator = new NinjectConfigurator();
containerConfigurator.Configure(kernel);
}
I use .InRequestScope() because I want a EFDbContext instance per request.
My question is: When do I have to do EFDbContext.SaveChanges()? If I'm using one instance per request I think I have to save the changes at the end of the request, isn't it?
Where do I have to put EFDbContext.Commit()?
The way I do it, and have seen done other places, is to either commit in your business layer, or in your controller, after each transaction. That means sometimes SaveChanges() will be called more than once per request, but that shouldn't be a significant problem.
I've learned a lot from looking at the code for SocialGoal, which can be found here. It uses Autofac for DI, but it's the same principles as your own code. Maybe you can get some inspiration and answers there too.
I started using unity to inject stuff into one of my hubs. This works, but, when I resolve a hubcontext somewhere outside my hub it seems like i'm getting the wrong one. This is because when I try to send messages with it, connected clients don't get them.
Dependencyresolver:
public class SignalRUnityDependencyResolver : DefaultDependencyResolver, IDependencyResolver
{
private IUnityContainer _container;
public SignalRUnityDependencyResolver(IUnityContainer container)
{
_container = container;
}
public override object GetService(Type serviceType)
{
if (_container.IsRegistered(serviceType)) return _container.Resolve(serviceType);
else return base.GetService(serviceType);
}
public override IEnumerable<object> GetServices(Type serviceType)
{
if (_container.IsRegistered(serviceType)) return _container.ResolveAll(serviceType);
else return base.GetServices(serviceType);
}
}
What I register in my container:
container.RegisterType<MessageHub>(new InjectionConstructor(new EFAuthRepository()));
My hub:
public class MessageHub : Hub
{
IAuthRepository _repository;
public MessageHub(IAuthRepository repository)
{
_repository = repository;
}
How I resolve outside my hub:
var context = GlobalHost.ConnectionManager.GetHubContext<MessageHub>();
Is there anything else that needs to be registred?
You should use the instance of the resolver to get the IConnectionMananger from the container as explained here.
Althought it is for Ninject you can get the idea. (look at at the bottom). This ConnectionManager can get you the HubContext as you were used to via GlobalHost.
resolver.Resolve<IConnectionManager>().GetHubContext<MessageHub>()
We made a simple example to ilustrate this (Ninject and Unity examples using signalr) and you can check it out here. If you are eager for the setup, it is here. ;)
Let me know if it helps.
OK, so I've been working on this for hours. I've found a couple of posts here, but nothing that actually resolves the problem. So, let me try it again...
I have an MVC2 app using Ninject and a custom membership provider.
If I try and inject the provider using the ctor, I get an error: 'No parameterless constructor defined for this object.'
public class MyMembershipProvider : MembershipProvider
{
IMyRepository _repository;
public MyMembershipProvider(IMyRepository repository)
{
_repository = repository;
}
I've also been playing around with factories and Initialize(), but everything is coming up blanks.
Any thoughts/examples?
The Membership provider model can only instantiate a configured provider when it has a default constructor. You might try this using the Service Locator pattern, instead of using Dependency Injection. Example:
public class MyMembershipProvider : MembershipProvider
{
IMyRepository _repository;
public MyMembershipProvider()
{
// This example uses the Common Service Locator as IoC facade, but
// you can change this to call NInject directly if you wish.
_repository = ServiceLocator.Current.GetInstance<IMyRepository>;
}
This is how I was able to do this:
1) I created a static helper class for Ninject
public static class NinjectHelper
{
public static readonly IKernel Kernel = new StandardKernel(new FooServices());
private class FooServices : NinjectModule
{
public override void Load()
{
Bind<IFooRepository>()
.To<EntityFooRepository>()
.WithConstructorArgument("connectionString",
ConfigurationManager.ConnectionStrings["FooDb"].ConnectionString);
}
}
}
2) Here is my Membership override:
public class FooMembershipProvider : MembershipProvider
{
private IFooRepository _FooRepository;
public FooMembershipProvider()
{
NinjectHelper.Kernel.Inject(this);
}
[Inject]
public IFooRepository Repository
{
set
{
_FooRepository = value;
}
}
...
With this approach it doesn't really matter when the Membership provider is instantiated.
I had the same problem at the exact same spot in the book. It wasn't until later on in the book that I noticed there were two separate web.config files. I initially placed my connectionString key in the wrong web.config file. It wasn't until I placed the connectionString in the correct web.config file that the 'no parameterless constructor' error went away.
I have the following code in my ASP.NET project
public sealed class IoC
{
private static readonly IDependencyResolver resolver =
Service.Get("IDependencyResolver") as IDependencyResolver;
static IoC()
{
}
private IoC()
{
}
public static IDependencyResolver Container
{
get
{
return resolver;
}
}
}
public static class Service
{
public static object Get(string serviceName)
{
// Code to create and return instance...
}
}
Is IoC.Container going to be thread safe?
Initialization of static fields is thread-safe: that is, the .NET runtime guarantees that your field will be initialized only once in the program, no matter how many threads access it and in what order.
As Andrey points out, the Service.Get method itself needs to be thread-safe.
IoC itself looks ok, but the whole structure will not be thread-safe if resolver is not thread safe. If you want to have resolver per thread you can use attribute [ThreadStatic]