Nearly all of the Ninject examples I've seen explain how to use it with ASP.NET MVC, which will automatically inject dependencies into controllers. How would I use Ninject manually though? Let's say I have a custom ActionResult:
public class JsonResult : ActionResult
{
[Inject] public ISerializer Serializer { get; set; }
public JsonResult(object objectToSerialize)
{
// do something here
}
// more code that uses Serializer
}
Then in my controller, I'm using JsonResult in a method like this:
public ActionResult Get(int id)
{
var someObject = repo.GetObject(id);
return new JsonResult(someObject);
}
As you can see, I'm instantiating the object myself, which sidesteps Ninject's injection, and Serializer will be null. However, doing it the following way doesn't seem quite right to me:
public ActionResult Get(int id)
{
var someObject = repo.GetObject(id);
return IoC.Kernel.Get<JsonResult>(someObject);
}
Because now there's not only a dependency on Ninject in the controller, but I also have to expose the Ninject kernel in a static class/singleton and ensure that objects that rely on injection are only created via kernel.
Is there a way to somehow configure Ninject to inject the dependency without relying on exposing the kernel? I'd like to be able to use the new keyword if at all possible.
Use a factory that gets the kernel injected: E.g.
public class ResultFactory : IResultFactory
{
public ResultFactory(IKernel kernel)
{
this.kernel = kernel;
}
public JsonResult CreateJsonResult(object obj)
{
var result = this.kernel.Get<JsonResult>();
result.ObjectToSerialize = obj;
return result;
}
}
Inject this factory into the controller and use it to create your action results.
I think you should turn your JsonResult inside out:
public class JsonResult : ActionResult
{
public ISerializer Serializer { get; private set; }
public object ObjectToSerialize { get; set; }
public JsonResult(ISerializer serializer)
{
this.Serializer = serializer;
}
// more code that uses Serializer
}
This way you can retrieve the JsonResult with the container like this:
public ActionResult Get(int id)
{
var result = IoC.Kernel.Get<JsonResult>();
result.ObjectToSerialize = repo.GetObject(id);
return result;
}
Changing the signature of the JsonResult also enables Ninject to create an instance automatically. Because of this you can let Ninject automatically inject it as dependency into your controller:
public MyController(JsonResult result)
{
this.result = result;
}
public ActionResult Get(int id)
{
this.result.ObjectToSerialize = repo.GetObject(id);
return this.result;
}
Related
I am struggling with wiring dependencies through autofac in my WebApi 2 project. I have a following interface and class that i'd like to inject in my GET and POST controller actions,
public interface IRepository
{
IContext Context
{
get;
}
void SomeOperation();
}
public MyRepository : IRepository
{
IContext _context;
public MyRepository(IContext context)
{
_context = context;
}
public Context
{
get
{
return _context;
}
}
public void SomeOperation
{
// Perform some operation using _context;
}
}
I 'd like IRepository to be injected in controller like this,
public class MyController : ApiController
{
private readonly IRepository _repo;
public ApplicationsController(IRepository repo)
{
_repo = repo;
}
// GET: api/v1/Contexts({contextId})
public IHttpActionResult Get(string contextId)
{
_repo.SomeOperation();
}
}
IContext object to be injected in MyRepository has to be fetched from a factory, something like this
public class ContextFactory
{
Hashtable contextMap;
IContext Get(string contextId)
{
if contextMap.Contains(contextId)
return contextMap[contextId].Value;
else
{
IContextConfiguration configuration = ContextConfigurationFactory.Get(contextId);
IContext context = new ConcreteContext(configuration);
contextMap.Add[contextId, context];
return context;
}
}
}
I am not sure how to wire all the classes and convert logic in factory classes by injecting relationships through Autofac so that context id passed in url is passed to ContextConfigurationFactory.Get and instantiate ConcreteContext object when not found in hash and eventually Autofac injecting right context object in MyRepository before passing it on to Get action in the controller.
Let's simplify this a bit. What you're trying to do is:
Get the context ID from a route parameter.
Use that route parameter in the factory to create a context.
The rest seems pretty much peripheral - the repository, the controller, all that. The crux of the question is that you need to get a route parameter into your factory.
Given that, let's put together some simplified code:
public class ContextFactory
{
public IContext Get(string contextId)
{
return new Context(contextId);
}
}
public interface IContext
{
string Id { get; }
}
public class Context : IContext
{
public Context(string id)
{
this.Id = id;
}
public string Id { get; private set; }
}
That's basically what you have:
An IContext interface that things need.
A ContextFactory that is basically responsible for building these things.
A Context concrete implementation of IContext that is built by the factory.
I would probably do something like this:
var builder = new ContainerBuilder();
builder.RegisterType<ContextFactory>();
builder.Register(ctx =>
{
var routeData = HttpContext.Current.Request.RequestContext.RouteData;
var id = routeData.Values["contextId"] as string;
var factory = ctx.Resolve<ContextFactory>();
return factory.Get(id);
}).As<IContext>()
.InstancePerLifetimeScope();
Now when you resolve IContext it will use your factory, get the current context ID from route data, and pass it through the factory.
I will leave the following for you to look into:
What happens if the route parameter isn't there? (Autofac won't let you return null.)
What happens if the route parameter has invalid data?
The route parameter is pretty hackable, is this a security risk?
...and so on.
I want to use IOC with my service and I want to instead inject a class not an interface in the constructor as below in the services layer but I do not want to create a new object from the calling layer like var service = new InvoiceService(new ChangeInvoiceDueDateCommand()) instead I want to create something like this from my controller in MVC where the IInvoiceService is injected into the controller constructor but the problem I see is that
public InvoiceController(IInvoiceService invoiceService, IMapper mapper)
{
_invoiceService = invoiceService;
_mapper = mapper;
}
and then called like this
public ActionResult ChangeInvoiceDueDate(InvoiceChangeDueDateViewModel invoiceChangeDueDateViewModel )
{
var request = _mapper.Map<InvoiceChangeDueDateViewModel, ChangeInvoiceDuedateRequest>(invoiceChangeDueDateViewModel);
InvoiceChangeDueDateResponse response = _invoiceService.ChangeDueDate(request);
return View();
}
Service Layer
public class InvoiceService : IInvoiceService
{
private readonly ChangeInvoiceDueDateCommand _changeInvoiceDueDateCommand;
public InvoiceService(ChangeInvoiceDueDateCommand changeInvoiceDueDateCommand)
{
_changeInvoiceDueDateCommand = changeInvoiceDueDateCommand;
}
public InvoiceChangeDueDateResponse ChangeDueDate(ChangeInvoiceDuedateRequest invoiceChangeDueDateRequest)
{
_changeInvoiceDueDateCommand.Execute(invoiceChangeDueDateRequest);
return new InvoiceChangeDueDateResponse {Status = new Status()};
}
}
Command
public class ChangeInvoiceDueDateCommand : ICommand<ChangeInvoiceDuedateRequest>
{
private readonly IRepository<Invoice> _invoiceRepository;
readonly InvoiceDueDateChangeValidator _validator;
public ChangeInvoiceDueDateCommand(IRepository<Invoice> invoiceRepository)
{
_invoiceRepository = invoiceRepository;
_validator = new InvoiceDueDateChangeValidator();
}
public void Execute(ChangeInvoiceDuedateRequest request)
{
if (_validator.IsDuedateValid(request.NewDuedate))
{
Invoice invoice = _invoiceRepository.GetById(request.Id);
invoice.ChangedDueDate(request.NewDuedate);
_invoiceRepository.SaveOrUpdate(invoice);
}
else
{
throw new InvalidDueDateException();
}
}
}
ICommand
public interface ICommand<T> where T : IRequest
{
void Execute(T request);
}
IRequest
public interface IRequest
{
int Id { get; set; }
}
I worked it out. It was just a Windsor syntax issue. It ended up being as simple as registering the Command using the container.Register(Component.For<ChangeInvoiceDueDateCommand>());
I am building an EntityFramework/WebApi back end.
I want to decouple my WebApi from the Entity Framework, and utilize Dependency Injection so I can swap out the "data source" for the web API.
I have been looking at the Unit of Work and Repository patterns.
I also want to use breezejs.
The breezejs TempHire samples has been alot of help, so I will use this as an example for my question -
https://github.com/Breeze/breeze.js.samples/tree/master/net/TempHire
In this sample, on the data side we have the UnitOfWork class -
public class UnitOfWork
{
private readonly EFContextProvider<TempHireDbContext> _contextProvider;
public UnitOfWork()
{
_contextProvider = new EFContextProvider<TempHireDbContext>();
StaffingResources = new Repository<StaffingResource>(_contextProvider.Context);
Addresses = new Repository<Address>(_contextProvider.Context);
// .. etc.
}
public IRepository<StaffingResource> StaffingResources { get; private set; }
public IRepository<Address> Addresses { get; private set; }
// .. etc.
public SaveResult Commit(JObject changeSet)
{
return _contextProvider.SaveChanges(changeSet);
}
}
Then on the WebApi side, it uses it like this -
[BreezeController]
[Authorize]
public class ResourceMgtController : ApiController
{
private readonly UnitOfWork _unitOfWork = new UnitOfWork();
[HttpPost]
public SaveResult SaveChanges(JObject saveBundle)
{
return _unitOfWork.Commit(saveBundle);
}
// ... etc.
}
I would like to refactor to something like this, so that I could swap out the back end.
public class UnitOfWork : IUnitOfWork
public class ResourceMgtController : ApiController
{
private readonly IUnitOfWork _unitOfWork;
public ResourceMgtController(IUnitOfWork unitOfWork) {
this._unitOfWOrk = unitOfWork; // Dependency Injected...
}
// ... etc.
}
What I can't wrap my head around, is how I can make it generic. The breeze client needs a method like this -
[HttpPost]
public SaveResult SaveChanges(JObject saveBundle)
{
return _unitOfWork.Commit(saveBundle);
}
And I can't put this in IUnitOfWork -
SaveResult SaveChanges(JObject saveBundle)
And really keep it decoupled from breeze, be able to swap out the back end for another backend. Am I attempting the abstraction at the wrong point? I guess if I want breeze on the client I will need to couple it on the backend?
You clearly can define an interface with that method:
public interface IUnitOfWork {
...
SaveResult SaveChanges(JObject saveBundle); // no problem
}
I suspect that you are objecting to the fact that both SaveResult and JObject are classes defined by libraries (Breeze.ContextProvider and Newtonsoft.Json.Linq respectively) you'd rather not reference somewhere.
These references wouldn't bother me any more than I mind referencing System.Linq to get IQueryable. In fact, a test double of SaveResult (a public class of Breeze.ContextProvider) is trivially easy to construct. Here is its definition (and the definition of KeyMapping, its only non-native dependent type):
public class SaveResult
{
public List<object> Entities;
public List<KeyMapping> KeyMappings;
public List<object> Errors;
}
public class KeyMapping
{
public string EntityTypeName;
public object TempValue;
public object RealValue;
}
But if Breeze and Newtonsoft.Json references are that noxious to you and you're willing to surrender some type safety, you can always create the interface like this:
public interface IUnitOfWork {
...
object SaveChanges(object saveBundle); // no safety, no problem
}
Then in your concrete UnitOfWork you add a suitable overload:
public object IUnitOfWork.SaveChanges(object saveBundle)
{
return SaveChanges((JObject) saveBundle);
}
public SaveResult SaveChanges(JObject saveBundle)
{
return _contextProvider.SaveChanges(saveBundle);
}
... and Bob's your uncle.
Yes, I did try it (in DocCode); worked fine for me.
I have a method in HomeController, that I'm trying to access through URL, like this:
http://localhost/web/home/GetSmth
First time it works, but after refreshing page, I get this error:
The operation cannot be completed because the DbContext has been disposed.
As the title states, I'm trying to use Castle Windsor and DbContext per request.
public class Installer1 : IWindsorInstaller
{
public void Install(IWindsorContainer container, IConfigurationStore store)
{
container.Register(Classes.FromThisAssembly()
.BasedOn<IController>()
.LifestyleTransient()
);
var connString = ConfigurationManager.ConnectionStrings["MainDbContext"].ConnectionString;
container.Register(Component.For<MainDbContext>().DependsOn(Property.ForKey("conn").Eq(connString)).LifeStyle.PerWebRequest);
container.Register(Component.For<ISomeService>().ImplementedBy<SomeService>());
}
}
HomeController looks like this:
public class HomeController : Controller
{
private ISomeService _someService;
public HomeController(ISomeService someService)
{
_someService = someService;
}
public ActionResult Index()
{
return View();
}
public JsonResult GetSmth()
{
var data = _someService.GetData().ToList();
return Json(data, JsonRequestBehavior.AllowGet);
}
}
You are registering ISomeService with the default lifecycle, which is singleton. Once it's created, it will keep using the same DbContext. Simplest solution is to change its lifecycle to per request or transient.
container.Register(Component.For<ISomeService>()
.ImplementedBy<SomeService>()
.LifeStyle.PerWebRequest);
Trying to learn ASP MVC coming from Linux/LAMP background (in other words I'm a newb) ...
For some reason I can't seem to use a function defined in a controller in another controller.
Here's the function in my MessagesController.cs file:
public List<Message> GetMessagesById(string username)
{
return db.Messages.Where(p => p.user == username).ToList();
}
When I try to reference it:
using LemonadeTrader.Models;
using LemonadeTrader.Controllers; // added this to pull the Messages::getMesssagesById
...
ViewBag.messages = lemondb.Messages.GetMessagesById(Membership.GetUser().ProviderUserKey.ToString());
I get something along the lines of lemondb.Messages does not contain a method called GetMesssagesById.
How do I reference it?
You shouldn't be linking controller methods like this, not to mention that controllers shouldn't be performing data access directly. I would recommend you externalizing this function into a separate class/repository which could be used by both controllers.
Example:
public class MessagesRepository
{
public List<Message> GetMessagesById(string username)
{
return db.Messages.Where(p => p.user == username).ToList();
}
}
and then:
public class FooController: Controller
{
public ActionResult Index()
{
var db = new MessagesRepository()
ViewBag.messages = db.GetMessagesById(Membership.GetUser().ProviderUserKey.ToString());
return View();
}
}
public class BarController: Controller
{
public ActionResult Index()
{
var db = new MessagesRepository()
ViewBag.messages = db.GetMessagesById(Membership.GetUser().ProviderUserKey.ToString());
return View();
}
}
OK, that's the first step. This code could be improved by decoupling the controllers from the repository by introducing an abstraction for this repository:
public interface IMessagesRepository
{
List<Message> GetMessagesById(string username);
}
public class MessagesRepository: IMessagesRepository
{
public List<Message> GetMessagesById(string username)
{
return db.Messages.Where(p => p.user == username).ToList();
}
}
then you could use constructor injection for those controllers:
public class FooController: Controller
{
private readonly IMessagesRepository _repository;
public class FooController(IMessagesRepository repository)
{
_repository = repository;
}
public ActionResult Index()
{
ViewBag.messages = _repository.GetMessagesById(Membership.GetUser().ProviderUserKey.ToString());
return View();
}
}
public class BarController: Controller
{
private readonly IMessagesRepository _repository;
public class BarController(IMessagesRepository repository)
{
_repository = repository;
}
public ActionResult Index()
{
ViewBag.messages = _repository.GetMessagesById(Membership.GetUser().ProviderUserKey.ToString());
return View();
}
}
finally you would configure your DI framework to pass the corresponding implementation into those controllers.
I would also recommend you replacing this ViewBag with a strongly typed view model:
public class MyViewModel
{
public List<Message> Messages { get; set; }
}
and then:
public ActionResult Index()
{
var model = new MyViewModel
{
Messages = _repository.GetMessagesById(Membership.GetUser().ProviderUserKey.ToString())
};
return View(model);
}
Place GetMessageById (and all other methods needed for accessing messages) to separate class and use the class everywhere you need to get Message data.
MessageService service = new MessageService();
ViewBag.messages = service.GetMessagesById(...);