Ninject Conditional Binding to Change Scope - asp.net-mvc

Using Ninject in a MVC4 application with the MVC3 Ninject Extension, when binding to a repository (a DbContext), I want to use InRequestScope for Controllers, and InSingletonScope when the same repository is used within a custom MembershipProvider.
I want to do this:
kernel.Bind<IRepo>().To<Repo>().InRequestScope();
kernel.Bind<IRepo>().To<Repo>().WhenInjectedInto<MembershipHelper>()
.InSingletonScope();
So that each web request to a controller gets a fresh instance of the repo, while the MembershipProvider maintains a re-usable connection to the repo.
This appears to work ok in a development environment, but how do I know which binding is being used? Is there a way to test that the scope is working correctly?

Yes, this is fine. Here's a very easy way to test it:
public interface IRepo { }
public class Repo : IRepo { }
public class MembershipHelper
{
private readonly IRepo _repo;
public MembershipHelper(IRepo repo)
{
_repo = repo;
}
public string GetId()
{
return _repo.GetHashCode().ToString();
}
}
public class HomeController : Controller
{
private readonly IRepo _repo;
private readonly MembershipHelper _helper;
public HomeController(IRepo repo, MembershipHelper helper)
{
_repo = repo;
_helper = helper;
}
public ActionResult Index()
{
return Content(_repo.GetHashCode().ToString() + " " + _helper.GetId());
}
}
Now navigate to /home/index and observe the 2 hashcodes. The first changes on each request whereas the second remains the same.

Related

Autofac Dependency Injection - Set public property

I am building the asp.net WebAPI project and have used Autofac as IOC. Now i am doing constructor based injection and calls the various methods of the business class from the controller class.
Now i want to pass some additional data into the business class via the public property IncomingUser such as this one :-
My interface looks like this :-
public interface IUserManager
{
string IncomingUser { set; get; }
Task<List<String>> GetUserPofiles(string Name);
}
This readonly property IncomingUser will be used inside various methods defined under the class UserManager.
public class UserManager : IUserManager
{
public string IncomingUser { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }
public async Task<List<String>> GetUserPofiles(string Name)
{
......Business Logic for the method......
}
}
From the API controller, i am setting the DI like this :-
public class myAPIController : ApiController
{
IUserManager _Manager;
public myAPIController(IUserManager Mang)
{
_Manager = Mang;
}
}
Please suggest, how should i set the property IncomingUser from the API controller class with the help of autofac DI or another way.

Entity Framework DbContext Lifetime in ASP.NET MVC Using Ninject?

I have the following unit of work pattern set up for an MVC 5 application using Entity Framework. The unit of work has all the repos defined as follows so that they are all using the same dbcontext and it has one save method to co-ordinate the transaction using the same context:
public class UnitOfWork : IUnitOfWork
{
private readonly ApplicationDbContext _context;
public IProductRepository ProductRepository { get; private set; }
public ICustomerRepository CustomerRepository { get; private set; }
// Other reposistories
public UnitOfWork(ApplicationDbContext context)
{
_context = context;
ProductRepository = new ProductRepository(_context);
CustomerRepository = new CustomerRepository(_context);
// Other reposistories
}
public void Complete()
{
_context.SaveChanges();
}
}
This is an example of my repo. The reason for using repos is for code re-use so that I'm not duplicating queries inside different controllers.
public class ProductRepository : IProductRepository
{
private readonly ApplicationDbContext _context;
public ProductRepository(ApplicationDbContext context)
{
_context = context;
}
public Product GetProduct(int productId)
{
return _context.Ticket.SingleOrDefault(p => p.Id == productId);
}
public void Add(Product product)
{
_context.Product.Add(product);
}
// Other methods
}
I inject the unit of work class in my controller as follows using Ninject:
public class ProductsController : Controller
{
private readonly IUnitOfWork _unitOfWork;
private readonly IFileUploadService _FileUploadService;
public ProductsController(IUnitOfWork unitOfWork,
IFileUploadService fileUploadService)
{
_unitOfWork = unitOfWork;
_FileUploadService = fileUploadService;
}
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Create(CreateEditProductViewModel viewModel)
{
var product = new Product
{
// Do stuff
};
_unitOfWork.ProductRepository.Add(product);
// Call file upload service
_fileUploadService.Upload();
_unitOfWork.Complete();
}
}
This unit of work set up works fine if all I'm using are repos that are defined in the unit of work class. But now I want to use a service class to process some additional application logic and then the unit of work is committed in the controller action. If I define the class as follows it will be using a different instance of the context, In which case how would you co-ordinate a transaction where the service layers is ending up with a different context?
public class FileUploadService : IFileUploadService
{
private readonly IUnitOfWork _unitOfWork;
public FileUploadService(IUnitOfWork unitOfWork)
{
_unitOfWork = unitOfWork;
}
public uploadResult Upload()
{
// Some stuff
var uploadedFile = new UploadedFile
{
//some stuff
};
_unitOfWork.UploadedFileRepository.Add(uploadedFile);
}
}
I've done quite a bit of research online and I'm unable to find any resource that provides a practical example to solve this problem. I've read quite a bit of stuff on ditching unit of work and repos and simply using entity frameworks dbset. However as explained above the purpose of using
repos is to consolidate queries. My questions is how do I co-ordinate the unit of work with a service class.
I would like the service to use the same context so that it can access the repositories it needs to work with, and let the controller (client code) commit the operation when it see fits.
* UPDATE *
In my DI Container I resolve all interfaces using the following snippet:
private static IKernel CreateKernel()
{
RegisterServices(kernel);
kernel.Bind<IUnitOfWork>().To<UnitOfWork>().InRequestScope();
// default binding for everything except unit of work
kernel.Bind(x => x.FromAssembliesMatching("*")
.SelectAllClasses()
.Excluding<UnitOfWork>()
.BindDefaultInterface());
return kernel;
}
Would adding the line kernel.Bind<IUnitOfWork>().To<UnitOfWork>().InRequestScope(); ensure that no more than one ApplicationDbContext is created, even if the request ends up hitting multiple controllers or service layers that all require an IUnitOfWork (ApplicationDbContext)?
If you are using MVC, then your unit of work is your web request. If I were you I'd ditch the UOW implementation and just make sure you dbcontext is instantiated in the Application_BeginRequest. Then I'd stuff it into the HttpContext for safe keeping. On Application_EndRequest, I dispose of the DbContext.
I would move the save to your repository.
I'd create a [Transaction] attribute that would maintain a TransactionScope something like this:
[AttributeUsage(AttributeTargets.Method | AttributeTargets.Class)]
public class TransactionAttribute : ActionFilterAttribute
{
private TransactionScope Transaction { get; set; }
public override void OnActionExecuting(ActionExecutingContext filterContext)
{
Transaction = new TransactionScope( TransactionScopeOption.Required);
}
public override void OnActionExecuted(ActionExecutedContext filterContext)
{
if (filterContext.Exception == null)
{
Transaction.Complete();
return;
}
Transaction.Dispose();
}
}
You can then just tag your controller methods with [Transaction].
I'm just spitballing here, but I do something similar with NHibernate instead of EF and it works out nicely for me.
The InRequestScope() will create a new instance of the bound type on every new web request, and at the end of that web request, it will Dispose that instance if it is disposable.
I am not sure how are you passing the ApplicationDbContext into your UnitOfWork. I am assuming that you use Ninject for this injection too. Just make sure that you bind your ApplicationDbContext using the InRequestScope()Bind.To().InRequestScope();.
This way, your ApplicationDbContext instance will be created once per request and disposed at the end.
Also, the use of InRequestScope is for types that are disposable, so you can also release resoruces in the Dispose method of your UnitOfWork method too.

Using the Repository Pattern and DI to switch between SQL and XML ASP.Net MVC

i have XMLProductRepository and SQLProductRepository. now how could i switch between them dynamically. i am new in DI. so searching google for the same and found a link which discuss a bit. but still do not understand on what basis the repository will be changed and how. here is the code
public interface IProductRepository
{
IEnumerable<Product> GetAll();
Product Get(int id);
Product Add(Product item);
void Remove(int id);
bool Update(Product item);
}
public class XMLProductRepository : IProductRepository
{
public XMLProductRepository() {}
public IEnumerable<Product> GetAll() {}
public Product Get(int id) {}
public Product Add(Product item) {}
public void Remove(int id) {}
public bool Update(Product item) {}
}
public class SQLProductRepository : IProductRepository
{
public SQLProductRepository() {}
public IEnumerable<Product> GetAll() {}
public Product Get(int id) {}
public Product Add(Product item) {}
public void Remove(int id) {}
public bool Update(Product item) {}
}
Unity.Mvc3 is using as Di
public static class Bootstrapper
{
public static void Initialise()
{
var container = BuildUnityContainer();
DependencyResolver.SetResolver(new UnityDependencyResolver(container));
}
private static IUnityContainer BuildUnityContainer()
{
var container = new UnityContainer();
//Register the repository
container.RegisterType<IProductRepository, SQLProductRepository>();
return container;
}
}
protected void Application_Start()
{
AreaRegistration.RegisterAllAreas();
WebApiConfig.Register(GlobalConfiguration.Configuration);
FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
RouteConfig.RegisterRoutes(RouteTable.Routes);
BundleConfig.RegisterBundles(BundleTable.Bundles);
AuthConfig.RegisterAuth();
Bootstrapper.Initialise();
}
public class HomeController : Controller
{
private readonly IProductRepository productRepository;
public HomeController(IProductRepository productRepository)
{
this.productRepository = productRepository;
}
i understand the code that dynamically SQLProductRepository instance is getting injecting into controller. so my question is how to inject XMLProductRepository ?
i want to design something in such a way based on url dependency will be injected.
how to achieve it. looking for guide line. thanks
One possible solution is to inject an IProductRepositoryFactory instead of IProductRepository itself. It would look like this:
interface IProductRepositoryFactory
{
IProductRepository GetRepository(string url);
}
Then your HomeController would look like this:
public class HomeController : Controller
{
private readonly IProductRepositoryFactory productRepositoryFactory;
public HomeController(IProductRepositoryFactory productRepositoryFactory)
{
this.productRepositoryFactory = productRepositoryFactory;
}
}
This way, you'll be able to get required implementation of IProductRepository in your controller action at runtime — all you need is to implement the required logic in the IProductRepositoryFactory.GetRepository(url) method.
Here's a controller action example (note that getting current request URL in such a way makes this method less testable):
public Product Get(string id)
{
return productRepositoryFactory
.GetRepository(Request.Url.ToString())
.GetById(id);
}
UPD: The following is an example implementation of IProductRepositoryFactory. Just implement your own decision-making logic that returns an appropriate instance of IProductRepository based on the URL:
public class ProductRepositoryFactory : IProductRepositoryFactory
{
public IProductRepository GetRepository(string url)
{
if (url.Contains("xml")) { return new XMLProductRepository(); }
if (url.Contains("sql")) { return new SQLProductRepository(); }
throw new ArgumentException("url");
}
}
I don't know where you got the code from, perhaps this question, but the two implementations of IProductRepository that you show have two purposes.
SQLProductRepository will read and write data from and to the database.
XMLProductRepository can read XML and maybe write files.
When running code in a unit test, you generally don't want to connect to a database, but you do sometimes want to use data in a unit test. That's where the XML repository comes in handy. You prepare a data set in XML files that you can commit to version control, you inject another implementation of the requested interface - namely one that reads the XML file - and you don't need a database anymore.
That's why you configure your DI container to inject the SQLProductRepository, while in unit tests you or the DI container will provide an XMLProductRepository when the application requests an IProductRepository.
Now if you say that your controller, your business logic, is to choose SQLProductRepository for one particular request, based on the URI, and XMLProductRepository for the other, then using IProductRepository for that purpose is wrong. That is a problem that should not be solved using your DI container.
Introduce two new interfaces instead and apply those to the repositories:
public interface ISqlProductRepository : IProductRepository
{
}
public interface IXmlProductRepository : IProductRepository
{
}
SQLProductRepository : ISqlProductRepository
XMLProductRepository : IXmlProductRepository
And register and inject those:
// Application startup
container.RegisterType<ISqlProductRepository, SQLProductRepository>();
container.RegisterType<IXmlProductRepository, XMLProductRepository>();
// Controller
private readonly ISqlProductRepository _sqlProductRepository;
private readonly IXmlProductRepository _xmlProductRepository;
public HomeController(ISqlProductRepository sqlProductRepository, IXmlProductRepository xmlProductRepository)
{
_sqlProductRepository = sqlProductRepository;
_xmlProductRepository = xmlProductRepository;
}
public ActionResult SqlMethod1()
{
// use _sqlProductRepository
}
public ActionResult XmlMethod2()
{
// use _xmlProductRepository
}
Of course now you can't inject XMLProductRepository for SQLProductRepository anymore, but that's a problem easily solved using mocking.
Anyway based on your current streak of questions, you're trying to learn something about unit testing and dependency injection. Please pick up a decent book and stop tying pieces together from blog posts, which hardly ever explain everything you need to know.

DI for a Repository and Unit of Work pattern

Previously I have had parameterless repositories being injected into my MVC controllers:
ProjectRepository implementation:
public class ProjectRepository : EntityFrameworkRepository<Project>, IProjectRepository
{
public ProjectRepository()
{ }
}
UnityConfig.cs dependency resolution:
container.RegisterType<IProjectRepository, ProjectRepository>();
MVC Controller:
private IProjectRepository _projectRepository { get; set; }
public ProjectController(IProjectRepository projectRepository)
{
_projectRepository = projectRepository;
}
This worked great.
Now I have implemented a Unit of Work pattern into my repository classes so that I can commit transactional changes to data (especially when changes are being made to more than one repository).
The new ProjectRepository implementation accepts a IUnitOfWork in its constructor:
public class ProjectRepository : EntityFrameworkRepository<Project>, IProjectRepository
{
public ProjectRepository(IUnitOfWork unitOfWork): base(unitOfWork)
{ }
}
This means that multiple repositories can share the same IUnitOfWork and changes can be collectively committed using UnitOfWork.SaveChanges().
QUESTION:
How do I now use dependency injection to instantiate the repository with an instance of IUnitOfWork?
public ProjectController(IProjectRepository projectRepository, IUnitOfWork unitOfWork)
{
_projectRepository = projectRepository;
_unitOfWork = unitOfWork;
}
There could also be more than one repository injected into the controller. How can these all be instantiated with the same IUnitOfWork?
When you register your IUnitOfWork instance, use PerResolveLifetimeManager, this will ensure every dependency of IUnitOfWork within a single IUnityContainer.Resolve gets provided the same instance.
For example:
public class SomeDependency
{
}
public class Service
{
public Service(SomeDependency someDependency, SomeDependency someDependency2)
{
Console.WriteLine(someDependency == someDependency2);
}
}
public static void Main()
{
using(var container = new UnityContainer())
{
container.RegisterType<SomeDependency>(new PerResolveLifetimeManager());
container.Resolve<Service>();
}
}
This will output True to the Console.
See the page for Understanding Lifetime Managers for further details.

Ninject.MVC3, Pass DependencyResolver to service-layer?

In a MVC3-application with Ninject.MVC 2.2.0.3 (after merge), instead of injecting repostories directly into controllers I'm trying to make a service-layer that contain the businesslogic and inject the repostories there. I pass the ninject-DependencyResolver to the service-layer as a dynamic object (since I don't want to reference mvc nor ninject there). Then I call GetService on it to get repositories with the bindings and lifetimes I specify in NinjectHttpApplicationModule. EDIT: In short, it failed.
How can the IoC-container be passed to the service-layer in this case? (Different approaches are also very welcome.)
EDIT: Here is an example to illustrate how I understand the answer and comments.
I should avoid the service locator (anti-)pattern and instead use dependency injection. So lets say I want to create an admin-site for Products and Categories in Northwind. I create models, repositories, services, controllers and views according to the table-definitions. The services call directly to the repositories at this point, no logic there. I have pillars of functionality and the views show raw data. These bindings are configured for NinjectMVC3:
private static void RegisterServices(IKernel kernel)
{
kernel.Bind<ICategoryRepository>().To<CategoryRepository>();
kernel.Bind<IProductRepository>().To<ProductRepository>();
}
Repository-instances are created by ninject via two layers of constructor injection, in the ProductController:
private readonly ProductsService _productsService;
public ProductController(ProductsService productsService)
{
// Trimmed for this post: nullchecks with throw ArgumentNullException
_productsService = productsService;
}
and ProductsService:
protected readonly IProductRepository _productRepository;
public ProductsService(IProductRepository productRepository)
{
_productRepository = productRepository;
}
I have no need to decouple the services for now but have prepared for mocking the db.
To show a dropdown of categories in Product/Edit I make a ViewModel that holds the categories in addition to the Product:
public class ProductViewModel
{
public Product Product { get; set; }
public IEnumerable<Category> Categories { get; set; }
}
The ProductsService now needs a CategoriesRepository to create it.
private readonly ICategoryRepository _categoryRepository;
// Changed constructor to take the additional repository
public ProductsServiceEx(IProductRepository productRepository,
ICategoryRepository categoryRepository)
{
_productRepository = productRepository;
_categoryRepository = categoryRepository;
}
public ProductViewModel GetProductViewModel(int id)
{
return new ProductViewModel
{
Product = _productRepository.GetById(id),
Categories = _categoryRepository.GetAll().ToArray(),
};
}
I change the GET Edit-action to return View(_productsService.GetProductViewModel(id)); and the Edit-view to show a dropdown:
#model Northwind.BLL.ProductViewModel
...
#Html.DropDownListFor(pvm => pvm.Product.CategoryId, Model.Categories
.Select(c => new SelectListItem{Text = c.Name, Value = c.Id.ToString(), Selected = c.Id == Model.Product.CategoryId}))
One small problem with this, and the reason I went astray with Service Locator, is that none of the other action-methods in ProductController need the categories-repository. I feel it's a waste and not logical to create it unless needed. Am I missing something?
You don't need to pass the object around you can do something like this
// global.aspx
protected void Application_Start()
{
// Hook our DI stuff when application starts
SetupDependencyInjection();
}
public void SetupDependencyInjection()
{
// Tell ASP.NET MVC 3 to use our Ninject DI Container
DependencyResolver.SetResolver(new NinjectDependencyResolver(CreateKernel()));
}
protected IKernel CreateKernel()
{
var modules = new INinjectModule[]
{
new NhibernateModule(),
new ServiceModule(),
new RepoModule()
};
return new StandardKernel(modules);
}
So in this one I setup all the ninject stuff. I make a kernal with 3 files to split up all my binding so it is easy to find.
In my service layer class you just pass in the interfaces you want. This service class is in it's own project folder where I keep all my service layer classes and has no reference to the ninject library.
// service.cs
private readonly IRepo repo;
// constructor
public Service(IRepo repo)
{
this.repo = repo;
}
This is how my ServiceModule looks like(what is created in the global.aspx)
// ServiceModule()
public class ServiceModule : NinjectModule
{
public override void Load()
{
Bind<IRepo>().To<Repo>();
}
}
Seee how I bind the interface to the repo. Now every time it see that interface it will automatically bind the the Repo class to it. So you don't need to pass the object around or anything.
You don't need worry about importing .dll into your service layer. For instance I have my service classes in their own project file and everything you see above(expect the service class of course) is in my webui project(where my views and global.aspx is).
Ninject does not care if the service is in a different project since I guess it is being referenced in the webui project.
Edit
Forgot to give you the NinjectDependecyResolver
public class NinjectDependencyResolver : IDependencyResolver
{
private readonly IResolutionRoot resolutionRoot;
public NinjectDependencyResolver(IResolutionRoot kernel)
{
resolutionRoot = kernel;
}
public object GetService(Type serviceType)
{
return resolutionRoot.TryGet(serviceType);
}
public IEnumerable<object> GetServices(Type serviceType)
{
return resolutionRoot.GetAll(serviceType);
}
}

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