I am making a website using ASP.NET MVC and an onion architecture. I have the following architecture:
Domain : Entities / Domain Interfaces
Repository : Generic repository (for now) using Entity Framework Code First Approach
Service : Generic Service that calls the Repository
MVC
Now I am trying to create a method in my controller to start testing the methods I have implemented in Repository and Service, and I am having a hard time as to what I am allowed to create in this controller. I want to test a simple Get method in the Repository, but to do that I need GenericService object and GenericRepository object in my controller. To demonstrate what I mean here's a snippet of my GenericRepository(I will skip the interfaces):
public class GenericRepository<T> : IGenericRepository<T> where T : class
{
private readonly PrincipalServerContext context;
private DbSet<T> entities;
public Repository(PrincipalServerContext context)
{
this.context = context;
entities = context.Set<T>();
}
}
Now my GenericService:
public class GenericService<T> : IGenericService<T> where T : class
{
private IRepository<T> repository;
public GenericService(IRepository<T> repository)
{
this.repository = repository;
}
public T GetEntity(long id)
{
return repository.Get(id);
}
}
And finally, my question, am I allowed to create these objects in my controller as follows (using my dbcontext called PrincipalServerContext):
public class NavigationController : Controller
{
private IGenericService<DomainModelClassHere> domainService;
private IGenericRepository<DomainModelClassHere> domainRepo;
private PrincipalServerContext context;
public ActionResult MyMethod(){
context = new PrincipalServerContext();
domainRepo = new GenericRepository<DomainModelClassHere>(context);
domainService = new GenericService<DomainModelClassHere>(domainRepo);
if(domainService.GetEntity(1)==null)
return View("UserNotFound");//Just as an example
return View();
}
}
Is this allowed? According to Jeffrey Palermo, UI can depend on Service and Domain so I don't know about the Repository. Technically I am not using methods from repository, but I do need to add a reference to the project.
If I can't then how can I create a new GenericService if I don't have a GenericRepository? Is there a better way to instantiate my objects ?
EDIT I think the answer to my question resides in Startup.cs where I can put something like service.addScoped(typeof(IGenericRepository<>),typeof(GenericRepository<>));
but I 'm not sure about this, any ideas?
I'll answer this on my own if ever someone encounters the same problem. There are configuration methods we can use to create instances of classes when needed. In the Startup.cs file you have to add ConfigureServices(IServiceCollection services) method and inside there are several methods that can be applied to services to create these instances. For example you can use:
services.AddTransient(IGenericRepository, GenericRepository)
What is the difference between services.AddTransient, service.AddScope and service.AddSingleton methods in Asp.Net Core 1? (this link explains differences between methods).
AddTransient is good in my case because it creates an instance of an object through the whole lifespan of the application, which is what I need. This means UI is dependant on the rest of the solution, because Startup.cs needs to know about the Repositories as well as the Services.
A pretty good answer can be found here :Onion Architecture : Can UI depend on Domain.
Related
I understand the basics of DI in .NET Core, but I'm having trouble figuring out how to use it with multiple projects. Imagine I'm setting up a database context in the Startup class of ASP.NET Core:
public void ConfigureServices(IServiceCollection services)
{
services.AddDbContext<GalleryDb>();
}
I know how to access that context in an API controller:
public class AlbumController : Microsoft.AspNetCore.Mvc.Controller
{
private GalleryDb _ctx;
public AlbumController(GalleryDb ctx)
{
_ctx = ctx;
}
}
But what does one do when there are many layers and functions between the API controller and the data access class? Eventually the code reaches my repository class, which is the one that actually requires the context. It looks like this:
public class AlbumRepository
{
private GalleryDb _ctx;
public AlbumRepository(GalleryDb ctx)
{
_ctx = ctx;
}
public void Save(AlbumEntity entity)
{
// Use _ctx to persist to DB.
}
}
I understand that I could pass the context from the API entry point all the way down, but that seems like an anti-pattern because it means passing it as a parameter through multiple classes and functions that have no interest in it.
Instead, I'd like to do something like this at the point where I invoke the repository class:
public void Save(AlbumEntity album)
{
var ctx = DependencyResolver.GetInstance<GalleryDb>();
var repo = new AlbumRepository(ctx);
repo.Save(album);
}
I believe some DI frameworks have something like this, but I'm trying to figure out how to do it with native .NET Core 2.0. Is this possible? What is the best practice? I found one thread (ASP.NET Core DependencyResolver) talk about using IServiceProvider but the implication was that this was not a desirable solution.
I'm hoping whatever the solution is, I can extend it to apply to other DI classes like ASP.NET Identity's RoleManager and SignInManager.
The key breakthrough chris-pratt helped me understand is that the only way this works is to use DI through all the layers. For example, down in the data layer I get a DB context through DI:
public class AlbumRepository
{
private GalleryDb _ctx;
public AlbumRepository(GalleryDb ctx)
{
_ctx = ctx;
}
}
In the business layer I use DI to get a reference to the data layer:
public class Album
{
private AlbumRepository _repo;
public Album(AlbumRepository repo)
{
_repo = repo;
}
}
Then, in the web layer, I use DI to get a reference to the business layer class:
[Route("api/[controller]")]
public class AlbumController : Microsoft.AspNetCore.Mvc.Controller
{
private Album _album;
public AlbumController (Album album)
{
_album = album;
}
}
By using DI through every layer, the DI system is able to construct all the necessary classes at the point where they are needed.
This requirement has a profound impact on the architecture of an application, and I now realize that my initial hope to tweak an existing, non-DI app to start using DI for the DB context is a major undertaking.
I understand that I could pass the context from the API entry point all the way down, but that seems like an anti-pattern because it means passing it as a parameter through multiple classes and functions that have no interest in it.
No, that's not an anti-pattern. That's how you should do it. However, the bit about "classes and functions that have no interest in it" makes no sense.
Simply, if you're working with something like a repository that wraps a DbContext (a horrible idea, by the way, but we'll put a pin in that), then you shouldn't ever be dealing directly with that DbContext. Instead, you should be injecting your repository into your controllers and then simply let the context be injected into that:
public void ConfigureServices(IServiceCollection services)
{
services.AddDbContext<GalleryDb>();
services.AddScoped<AlbumRepository>();
}
Since ASP.NET Core knows how to inject GalleryDb, and AlbumRepository takes GalleryDb as a constructor param, you simply register AlbumRepository for injection as well (using a "scoped" or request lifetime).
Now, you can inject AlbumRepository the same way you're currently injecting the context:
public class AlbumController : Microsoft.AspNetCore.Mvc.Controller
{
private AlbumRepository _repo;
public AlbumController(AlbumRepository repo)
{
_repo = repo;
}
}
Where this starts to get tricky is when you have many repositories, especially if you have controllers that need to interact with several repositories. Eventually, your code will become a rat's nest of service config and injection boilerplate. However, at that point, you should really be employing the unit of work pattern as well, encapsulating all your repositories in one class that you can inject instead. But wait, oh yeah, that's what DbContext is already. It's a unit of work encapsulating multiple repositories, or DbSets. This is why you shouldn't being using the repository pattern in conjunction with Entity Framework. It's a pointless abstraction that does nothing but add additional and unnecessary entropy to your code.
If you want to abstract DbContext, then you should use something like the service layer pattern (not to be confused with the RPC bull excrement Microsoft refers to as the "service pattern") or the CQRS (Command Query Responsibility Segregation) pattern. The repository pattern is for one thing: abstracting away raw SQL. If you don't have raw SQL, you should not be implementing that pattern.
I am going to use SimpleInjector in MVC.5 application with WebAPI.2
Some methods of MVC controllers will create objects of repositories for CRUD operations.
Common approach on the Internet is a using interface of repository in MVC controller, like:
public class DashboardController : Controller
{
private readonly IDashboardRepository _repository;
public DashboardController (IDashboardRepository repository) {
_repository = repository;
}
[HttpPost]
public JsonData GetInfo()
{
return _repository.GetInfo();
}
...
Similar approach is recommended for WebAPI
However I would not like to pass IDashboardRepository into constructor of controller because of such reasons: I am sure that I will never mock implementation of repository. I do not need separate public interface for repository (current code base has no these interfaces and I'll need to change a lot of files to add them).
My repositories look like:
public class DashboardFunc : BaseFunc
{
public DashboardFunc(IApplicationStateProvider sp) :
base (sp)
{
}
public DashBoardData GetInfo()
{
...
I would like to use such code in controllers of MVC:
public class DashboardController : Controller
{
public DashboardController () {
}
[HttpPost]
public JsonData GetInfo()
{
DashboardFunc dashBoard = Global.MvcContainer.GetInstance<DashboardFunc>();
return Common.ToJson(dashBoard.GetInfo());
}
The same approach I would like for WebAPI controllers. The only difference is
DashboardFunc dashBoard = Global.WebApiContainer.GetInstance();
Is my modification (not using interface of repository in controller) of standard approach OK? Are there any potential issues that can arise in future that can lead architecture change?
Thank you!
Prevent falling back on calling Global.MvcContainer.GetInstance or any other form of Service Location
anti-pattern. There are a lot of downsides to this, even if you don't want to test that code. Downsides of using this are (among others):
You lose the ability for the container to change the given implementation for you; it makes your application less flexible.
You lose the ability for the container to diagnose the complete object graph for you.
You lose the ability to verify the configuration during app start or using an integration test.
You lose the ability to spot all the class's dependencies just by looking at a single line of code (the constructor).
So even when you don't need that interface, I would advice to still use constructor injection and do the following:
public class DashboardController : Controller {
private readonly DashboardFunc dashboard;
public DashboardController(DashboardFunc dashboard) {
this.dashboard = dashboard;
}
[HttpPost]
public JsonData GetInfo() {
return Common.ToJson(this.dashBoard.GetInfo());
}
}
I have an asp.net-mvc website and i am using ninject for IOC and nhibernate for my ORM mapping
Here is my IOC binding code:
internal class ServiceModule : NinjectModule
{
public override void Load()
{
Bind(typeof(IIntKeyedRepository<>)).To(typeof(Repository<>)).InRequestScope();
}
}
and here is an example of how I am doing IOC into my controller code:
public FAQController(IIntKeyedRepository<FAQ> faqRepository, IUnitOfWork unitOfWork)
{
_faqRepository = faqRepository;
_unitOfWork = unitOfWork;
}
The issue is that up until now, each controller had a single table that it was pointing to so i only needed on repository class passed into it...
Now, I have a number of tables and classes that are all just have 2 fields:
Id
Name
for each of these classes, i simply inherit from a base class called:
BaseModel
which is just:
public class BaseModel
{
public virtual string Name { get; set; }
public virtual int Id { get; set; }
}
I want to have one:
StaticDataController
class that can do all of the CRUD for every class that simply inherits from BaseModel (with no extra fields)
The dumb simple way would be to do this:
private readonly IIntKeyedRepository<Object1> _object1Repository;
private readonly IIntKeyedRepository<Object2> _object2Repository;
private readonly IIntKeyedRepository<Object3> _object3Repository;
private readonly IIntKeyedRepository<Object4> _object4Repository;
private readonly IIntKeyedRepository<Object5> _object5Repository;
public StaticDataController(IIntKeyedRepository<Object1> obj1Repository, IIntKeyedRepository<Object2> obj2Repository, IIntKeyedRepository<Object3> obj3Repository, IIntKeyedRepository<Object4> obj4Repository, IIntKeyedRepository<Object5> obj5Repository)
{
_obj1Repository= obj1Repository;
_obj2Repository= obj2Repository;
_obj3Repository= obj3Repository;
_obj4Repository= obj4Repository;
_obj5Repository= obj5Repository;
}
Since I am passing the table in as a parameter to my methods, I would have to have some switch statement in my controller to get the right repository class based on the string of the parameter.
I assume there must be a much more elegant way to support what I am trying to do so I wanted to see if there is any best practice here (controller inheritance, reflection, etc.)?
If you need to do this it means that your controller does too many things and a strong indication that it requires a service layer. In this case I deport those repositories into the service layer. So my controller takes a service instead of multiple repositories:
private readonly IStatisticDataService _service;
public StaticDataController(IStatisticDataService service)
{
_service = service;
}
The service has business that could be composed of multiple atomic repository CRUD methods.
I know that you might say: yes, but now I have to inject all those repositories into the implementation of the IStatisticDataService interface. Yes, but it would make more sense to aggregate those atomic CRUD operations into the service layer rather than the controller.
But if need 5 or more repositories in order to perform a some business operations, maybe you have to rethink your domain architecture. Probably you could use composition in your domain models and define relations between them in order to reduce the number of repositories. It's difficult to provide more concrete advice without knowing the specifics of your domain.
Now, I have a number of tables and classes that are all just have 2 fields:
Great, make them derive all from the same base domain model and have a single repository to serve them. You could use descriminator columns, etc...
Darin is absolutely right. I'd just like to add though, if you're using MVC 3, you should be using the Ninject.MVC3 nuget package rather than creating your own Service Module.
As Mark Seemann mentioned: "It's quite OK, but once you feel that the Controller becomes too cluttered, you can refactor its dependencies to an Aggregate Service."
Look at: BestPractices: Is it acceptable to use more than one repository in a MVC-Controller?
I have the following problem - or rather, an urgent need for valuable advice - with Microsoft MVC. A certain action from the client leads to the creation of:
A remark in the table Remarks
An entry in the table for HourRegistrations
An entry in the changelog for Tickets
I use a service layer for business actions and repositories for CRUD actions. The problem is that I at times need to connect objects from different DataContexts so I suppose I use a flawed design. Recently we have started to remove all business logic from our controllers and repositories and this is one of the first things I run into.
Example:
BLogic.AddRemarks(Ticket t, ...)
{
Remark r = _remarksRepository.Create();
r.Ticket = t;
_remarksRepository.Add(r);
_remarksRepository.Save();
}
This triggers kBOOM since the Ticket is fetched in the controller using the repository. So Remark r and Ticket t do not share the same data context.
I can alter the signature of the method and provide an int TicketId, but that doesn't feel right. Besides, I then get similar problems further down the line.
My repositories are created at the constructor of the service class. Perhaps I must create them at the start of a method? Even then, I must often transfer Ids instead of the true objects.
My suggestion is to use dependeny injection (or inversion of control - depends how would you like to call it). I use myself castle windor. Really simple to integrate with mvc.net. read more
When IoC is up and running create ContextManager. Somethig like this:
public class ContextManager : IContextManager
{
private XContext context;
public XContext GetContext()
{
return context ?? (context = XContext.Create());
}
}
Set IContextManager lifestyle as perwebrequest and you got yourself context that you can access from repositories and services. and it's same per one request.
EDIT
You also have to create your own controllerFactory
then you can use your services and repositories like this:
public class MyController : Controller
{
public ISomeService SomeService { get; set; }
public IContextManager ContextManager { get; set; }
...
}
You dont have to create new instances for services and repositories and you can manage those objects lifestyle from configuration. Most reasonable would be singleton
What is the best way to manage the context of Entity Framework when using MVC application?
I am using a Repository/Service pattern.
Edit
After looking through some of these questions: stackoverflow.com/users/587920/sam-striano, I am more confused then before. Some say use the context per repository, but wht if I want to use multiple repositories in one controller method?
And to follow good separation design, how do you use UnitOfWork in the MVC app with out making it dependent on EF? I want to be able to unit test my controllers, model, services, etc. using a mock context?
Use a Dependency Injector/Inversion of Control framework like:
Ninject
Autofac
StructureMap
Unity
Using an IoC container, you can tell it how to manage a single data context (most commonly, per request). When you set the data context to per request, the container will auto-magically give any class that needs a data context the same data context per request.
Here is a good article on setting up Ninject.
What your code will most likely end up looking like, assuming you're using a generic repository:
Ninject Module:
public class NinjectRegistrationModule : NinjectModule
{
public override void Load()
{
Bind<MyDataContext>().ToSelf().InRequestScope();
Bind(typeof(RepositoryImplementation<>)).ToSelf().InRequestScope();
}
}
Generic Repository:
public RepositoryImplementation<T> : IRepository<T> where T : class
{
MyDataContext _dataContext;
public RepositoryImplementation<T>(MyDataContext dataContext)
{
_dataContext = dataContext;
}
// bunch of methods that utilize _dataContext
}
Service Class:
public class MyServiceClass
{
IRepository<SomeEntity> _someEntityRepository;
public MyServiceClass(IRepository<SomeEntity> someEntityRepository)
{
_someEntityRepository = someEntityRepository;
}
// do stuff with _someEntityRepository = someEntityRepository;
}
Controller:
public class MyController
{
MyServiceClass _myServiceClass;
public MyController(MyServiceClass myServiceClass)
{
// Ninject will auto-magically give us a myServiceClass
// which will Ninject will inject a repository into MyServiceClass's constructor
_myServiceClass = myServiceClass;
}
public ActionResult MyAction()
{
// use _myServiceClass to do stuff
return View();
}
}
If your functionality is straight forward, then you should create a new ObjectContext in each Repository. They are cheap to instantiate.
If this creates a conflict, you can use a Unit of Work pattern as was suggested in the comment.
I would advise that you be extremely cautious when integrating an ObjectContext or DataContext with a DI container. Many do not use the appropriate scope for their life cycle by default.