I have MVC5 application and i am using Unity as IOC container. I am registering all the components as shown below. Everything was working fine until i introduced
new class MyAccount into MyDomainService.
Now when unity try to resolve HomeController -> MyDomainService -> MyAccount i get error
Value cannot be null. Parameter name: String
well MyAccount constructor does not have any parameter
public class MyAccount
{
public MyAccount()
{
}
}
public class MyDomainService:IDisposable
{
private IGenericRepository _repository;
private MyAccount _myAccount;
// it works if i remove MyAccount from the constructor
public MyDomainService(IGenericRepository repository, MyAccount MyAccount)
{
_repository = repository;
_myAccount = MyAccount;
}
}
public static class UnityConfig
{
public static void RegisterComponents()
{
var container = new UnityContainer();
container.RegisterType<MyDomainService, MyDomainService>(new HierarchicalLifetimeManager());
container.RegisterType<IGenericRepository, GenericRepository>(new HierarchicalLifetimeManager());
container.RegisterType<DbContext, MYDbContext>(new HierarchicalLifetimeManager());
container.RegisterType<MyAccount, MyAccount>();
// MVC5
DependencyResolver.SetResolver(new Unity.Mvc5.UnityDependencyResolver(container));
UnityServiceLocator locator = new UnityServiceLocator(container);
ServiceLocator.SetLocatorProvider(() => locator);
}
}
public class HomeController:Controller
{
MyDomainService _service;
public HomeController(MyDomainService service)
{
_service = service;
}
}
This is not how Unity DependencyInjection works out of the box.
You should always accept only DependencyInjection entities to the constructor, and only if the entire class (e.g MyDomainService) can not live without any of the passes dependencies.
If DomainService is:
Strongly depended in both IGenericRepository and MyAccount then you should consider making MyAccount also registered at the IOC container(and redesign the class accordingly).
Strongly depended only in IGenericRepository or MyAccount(after redesign) then you should pass the constructor only the one that is depended and pass the methods the used depended entities.
For example
public DomainService(IGenericRepository genericRepository) { ... }
public void Method1(MyAccount account) { .. }
public void AnotherExampleMethod2(AnotherDependedClass anotherClass, int justANumber) { .. }
Related
We have a ASP.NET project, and we use AutoFac to DI.
We have a Service layer with all database queries and we need to make some queries in a static class.
This is how we register the dependencies in the Global.asax:
public class Dependencies
{
public static void RegisterDependencies()
{
var builder = new ContainerBuilder();
builder.RegisterControllers(typeof(MvcApplication).Assembly).PropertiesAutowired();
builder.RegisterModule(new ServiceModule());
builder.RegisterModule(new EfModule());
var container = builder.Build();
DependencyResolver.SetResolver(new AutofacDependencyResolver(container));
}
}
public class ServiceModule : Autofac.Module
{
protected override void Load(ContainerBuilder builder)
{
builder.RegisterAssemblyTypes(Assembly.Load("MyApp.Service")).Where(t => t.Name.EndsWith("Service")).AsImplementedInterfaces().InstancePerLifetimeScope();
}
}
public class EfModule : Autofac.Module
{
protected override void Load(ContainerBuilder builder)
{
builder.RegisterType(typeof(myDataContext)).As(typeof(IMyContext)).InstancePerLifetimeScope();
}
}
And this is how we access in the controller:
public class SomeController : Controller
{
private readonly IService1 _service1;
private readonly IService2 _service2;
public SomeController(IService1 service1, IService2 service2)
{
_service1 = service1;
_service2 = service2;
}
public ActionResult Index()
{
var service = _service1.GetAll();
...
return View(searchModel);
}
}
Now we need to retrieve data from the database in a static class, so we have to call our service layer, but we don't know how to do it...we have seen this, but I don't know if it is correct, but it works.
public static Test ()
{
...
var service1 = DependencyResolver.Current.GetService<IService1>();
...
}
Also, how it would be in both, non-static and static classes?
Thanks in advance.
The problem is I have to call many of those classes from different places and I don't want to depend on having the service in order to call the class, I'd like the class to take care of everything.
In this case you should register your class with Autofac so that it gets its dependencies injected:
builder.RegisterType<MyClass>();
If the class is used several times during a single request it might be useful to register it using InstancePerLifetimeScope(), but that depends on your overall architecture. See this link to the Autofac documentation for more information.
Of course you have to change your class so that the methods are not static any more and add an constructor to get the dependencies:
public class MyClass
{
private readonly IService1 _service1;
public MyClass(IService1 service1)
{
_service1 = service1;
}
public void Test
{
// use the _service1 instance to do whatever you want
}
}
Now you can inject the MyClass dependency in your controller and use it without having to know anything about its internals or its dependencies:
public class SomeController : Controller
{
private readonly IService1 _service1;
private readonly IService2 _service2;
private readonly MyClass _myClass;
public SomeController(IService1 service1, IService2 service2, MyClass myClass)
{
_service1 = service1;
_service2 = service2;
_myClass = myClass;
}
public ActionResult Index()
{
var service = _service1.GetAll();
...
_myClass.Test();
return View(searchModel);
}
}
I'm trying to implement IoC in my windows form application. My choice fell on Simple Injector, because it's fast and lightweight. I also implement unit of work and repository pattern in my apps. Here is the structure:
DbContext:
public class MemberContext : DbContext
{
public MemberContext()
: base("Name=MemberContext")
{ }
public DbSet<Member> Members { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();\
}
}
Model:
public class Member
{
public int MemberID { get; set; }
public string Name { get; set; }
}
GenericRepository:
public abstract class GenericRepository<TEntity> : IGenericRepository<TEntity>
where TEntity : class
{
internal DbContext context;
internal DbSet<TEntity> dbSet;
public GenericRepository(DbContext context)
{
this.context = context;
this.dbSet = context.Set<TEntity>();
}
public virtual void Insert(TEntity entity)
{
dbSet.Add(entity);
}
}
MemberRepository:
public class MemberRepository : GenericRepository<Member>, IMemberRepository
{
public MemberRepository(DbContext context)
: base(context)
{ }
}
UnitOfWork:
public class UnitOfWork : IUnitOfWork
{
public DbContext context;
public UnitOfWork(DbContext context)
{
this.context = context;
}
public void SaveChanges()
{
context.SaveChanges();
}
private bool disposed = false;
protected virtual void Dispose(bool disposing)
{
if (!this.disposed)
{
if (disposing)
{
context.Dispose();
}
}
this.disposed = true;
}
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
}
MemberService:
public class MemberService : IMemberService
{
private readonly IUnitOfWork unitOfWork;
private readonly IMemberRepository memberRepository;
public MemberService(IUnitOfWork unitOfWork, IMemberRepository memberRepository)
{
this.unitOfWork = unitOfWork;
this.memberRepository = memberRepository;
}
public void Save(Member member)
{
Save(new List<Member> { member });
}
public void Save(List<Member> members)
{
members.ForEach(m =>
{
if (m.MemberID == default(int))
{
memberRepository.Insert(m);
}
});
unitOfWork.SaveChanges();
}
}
In Member Form I only add a textbox to input member name and a button to save to database. This is the code in member form:
frmMember:
public partial class frmMember : Form
{
private readonly IMemberService memberService;
public frmMember(IMemberService memberService)
{
InitializeComponent();
this.memberService = memberService;
}
private void btnSave_Click(object sender, EventArgs e)
{
Member member = new Member();
member.Name = txtName.Text;
memberService.Save(member);
}
}
I implement the SimpleInjector (refer to http://simpleinjector.readthedocs.org/en/latest/windowsformsintegration.html) in Program.cs as seen in the code below:
static class Program
{
private static Container container;
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Bootstrap();
Application.Run(new frmMember((MemberService)container.GetInstance(typeof(IMemberService))));
}
private static void Bootstrap()
{
container = new Container();
container.RegisterSingle<IMemberRepository, MemberRepository>();
container.Register<IMemberService, MemberService>();
container.Register<DbContext, MemberContext>();
container.Register<IUnitOfWork, UnitOfWork>();
container.Verify();
}
}
When I run the program and add a member, it doesn't save to database. If I changed container.Register to container.RegisterSingle, it will save to database. From the documentation, RegisterSingle will make my class to be a Singleton. I can't using RegisterLifeTimeScope because it will generate an error
"The registered delegate for type IMemberService threw an exception. The IUnitOfWork is registered as 'Lifetime Scope' lifestyle, but the instance is requested outside the context of a Lifetime Scope"
1) How to use SimpleInjector in Windows Form with UnitOfWork & Repository pattern?
2) Do I implement the patterns correctly?
The problem you have is the difference in lifestyles between your service, repository, unitofwork and dbcontext.
Because the MemberRepository has a Singleton lifestyle, Simple Injector will create one instance which will be reused for the duration of the application, which could be days, even weeks or months with a WinForms application. The direct consequence from registering the MemberRepository as Singleton is that all dependencies of this class will become Singletons as well, no matter what lifestyle is used in the registration. This is a common problem called Captive Dependency.
As a side note: The diagnostic services of Simple Injector are able to spot this configuration mistake and will show/throw a Potential Lifestyle Mismatch warning.
So the MemberRepository is Singleton and has one and the same DbContext throughout the application lifetime. But the UnitOfWork, which has a dependency also on DbContext will receive a different instance of the DbContext, because the registration for DbContext is Transient. This context will, in your example, never save the newly created Member because this DbContext does not have any newly created Member, the member is created in a different DbContext.
When you change the registration of DbContext to RegisterSingleton it will start working, because now every service, class or whatever depending on DbContext will get the same instance.
But this is certainly not the solution because having one DbContext for the lifetime of the application will get you into trouble, as you probably already know. This is explained in great detail in this post.
The solution you need is using a Scoped instance of the DbContext, which you already tried. You are missing some information on how to use the lifetime scope feature of Simple Injector (and most of the other containers out there). When using a Scoped lifestyle there must be an active scope as the exception message clearly states. Starting a lifetime scope is pretty simple:
using (ThreadScopedLifestyle.BeginScope(container))
{
// all instances resolved within this scope
// with a ThreadScopedLifestyleLifestyle
// will be the same instance
}
You can read in detail here.
Changing the registrations to:
var container = new Container();
container.Options.DefaultScopedLifestyle = new ThreadScopedLifestyle();
container.Register<IMemberRepository, MemberRepository>(Lifestyle.Scoped);
container.Register<IMemberService, MemberService>(Lifestyle.Scoped);
container.Register<DbContext, MemberContext>(Lifestyle.Scoped);
container.Register<IUnitOfWork, UnitOfWork>(Lifestyle.Scoped);
and changing the code from btnSaveClick() to:
private void btnSave_Click(object sender, EventArgs e)
{
Member member = new Member();
member.Name = txtName.Text;
using (ThreadScopedLifestyle.BeginScope(container))
{
var memberService = container.GetInstance<IMemberService>();
memberService.Save(member);
}
}
is basically what you need.
But we have now introduced a new problem. We are now using the Service Locator anti pattern to get a Scoped instance of the IMemberService implementation. Therefore we need some infrastructural object which will handle this for us as a Cross-Cutting Concern in the application. A Decorator is a perfect way to implement this. See also here. This will look like:
public class ThreadScopedMemberServiceDecorator : IMemberService
{
private readonly Func<IMemberService> decorateeFactory;
private readonly Container container;
public ThreadScopedMemberServiceDecorator(Func<IMemberService> decorateeFactory,
Container container)
{
this.decorateeFactory = decorateeFactory;
this.container = container;
}
public void Save(List<Member> members)
{
using (ThreadScopedLifestyle.BeginScope(container))
{
IMemberService service = this.decorateeFactory.Invoke();
service.Save(members);
}
}
}
You now register this as a (Singleton) Decorator in the Simple Injector Container like this:
container.RegisterDecorator(
typeof(IMemberService),
typeof(ThreadScopedMemberServiceDecorator),
Lifestyle.Singleton);
The container will provide a class which depends on IMemberService with this ThreadScopedMemberServiceDecorator. In this the container will inject a Func<IMemberService> which, when invoked, will return an instance from the container using the configured lifestyle.
Adding this Decorator (and its registration) and changing the lifestyles will fix the issue from your example.
I expect however that your application will in the end have an IMemberService, IUserService, ICustomerService, etc... So you need a decorator for each and every IXXXService, not very DRY if you ask me. If all services will implement Save(List<T> items) you could consider creating an open generic interface:
public interface IService<T>
{
void Save(List<T> items);
}
public class MemberService : IService<Member>
{
// same code as before
}
You register all implementations in one line using Batch-Registration:
container.Register(typeof(IService<>),
new[] { Assembly.GetExecutingAssembly() },
Lifestyle.Scoped);
And you can wrap all these instances into a single open generic implementation of the above mentioned ThreadScopedServiceDecorator.
It would IMO even be better to use the command / handler pattern (you should really read the link!) for this type of work. In very short: In this pattern every use case is translated to a message object (a command) which is handled by a single command handler, which can be decorated by e.g. a SaveChangesCommandHandlerDecorator and a ThreadScopedCommandHandlerDecorator and LoggingDecorator and so on.
Your example would then look like:
public interface ICommandHandler<TCommand>
{
void Handle(TCommand command);
}
public class CreateMemberCommand
{
public string MemberName { get; set; }
}
With the following handlers:
public class CreateMemberCommandHandler : ICommandHandler<CreateMemberCommand>
{
//notice that the need for MemberRepository is zero IMO
private readonly IGenericRepository<Member> memberRepository;
public CreateMemberCommandHandler(IGenericRepository<Member> memberRepository)
{
this.memberRepository = memberRepository;
}
public void Handle(CreateMemberCommand command)
{
var member = new Member { Name = command.MemberName };
this.memberRepository.Insert(member);
}
}
public class SaveChangesCommandHandlerDecorator<TCommand>
: ICommandHandler<TCommand>
{
private ICommandHandler<TCommand> decoratee;
private DbContext db;
public SaveChangesCommandHandlerDecorator(
ICommandHandler<TCommand> decoratee, DbContext db)
{
this.decoratee = decoratee;
this.db = db;
}
public void Handle(TCommand command)
{
this.decoratee.Handle(command);
this.db.SaveChanges();
}
}
And the form can now depend on ICommandHandler<T>:
public partial class frmMember : Form
{
private readonly ICommandHandler<CreateMemberCommand> commandHandler;
public frmMember(ICommandHandler<CreateMemberCommand> commandHandler)
{
InitializeComponent();
this.commandHandler = commandHandler;
}
private void btnSave_Click(object sender, EventArgs e)
{
this.commandHandler.Handle(
new CreateMemberCommand { MemberName = txtName.Text });
}
}
This can all be registered as follows:
container.Register(typeof(IGenericRepository<>),
typeof(GenericRepository<>));
container.Register(typeof(ICommandHandler<>),
new[] { Assembly.GetExecutingAssembly() });
container.RegisterDecorator(typeof(ICommandHandler<>),
typeof(SaveChangesCommandHandlerDecorator<>));
container.RegisterDecorator(typeof(ICommandHandler<>),
typeof(ThreadScopedCommandHandlerDecorator<>),
Lifestyle.Singleton);
This design will remove the need for UnitOfWork and a (specific) service completely.
I am using Quartz .net v2.3.3.0 and Castle Windsor v3.3.0.0.
I have a job which is dependent on a Service
public class DemoJob : IJob
{
private readonly IService _Service;
public DemoJob(IService Service)
{
_Service = Service;
}
public void Execute(IJobExecutionContext context)
{
_Service.CallRepoMethod();
}
}
This is the service class which is in different project
public class Service: IService
{
public void CallRepoMethod()
{
Repo();
}
}
Everything works fine till now.
But as soon as I inject dependency in service class the job is not executed.
public class Service: IService
{
private readonly IRepository _repository;
Service(IRepository repository)
{
_repository = repository;
}
public void CallRepoMethod()
{
_repository.Repo();
}
}
IRepository is implemented by a simple Repository class with a single method.
Repository class is in different project and IService,Service and IRepository are in same project.
I don't get any error message but the job does not get executed. If i remove dependency from the Service class then everything works fine and jobs execute.
Here is how I have registered the dependencies
internal class CastleWindsorContainer : IContainer
{
public static WindsorContainer Container { get; private set; }
public CastleWindsorContainer()
{
Container = new WindsorContainer();
}
public void Register()
{
Container.Register(Component.For<IRepository>().ImplementedBy<Repository>().LifestyleTransient());
public Object Resolve(Type controllerType)
{
return Container.Resolve(controllerType);
}
public void Release(IController controller)
{
Container.Release(controller);
}
public void RegisterJobs(IJobFactory jobFactory)
{
Container.Register(Component.For<IJobFactory>().Instance(jobFactory).LifestyleTransient());
Container.Register(Component.For<IQuartzInitializer>().ImplementedBy<JobsConfig>().LifestyleTransient());
Container.Register(Component.For<IService>().ImplementedBy<Service>().LifestyleTransient());
Container.Register(Component.For<DemoJob>().ImplementedBy<DemoJob>().LifestyleTransient()
);
Container.Resolve<IQuartzInitializer>().RegisterJobs();
}
}
code in Global.asax
var container = new CastleWindsorContainer();
IJobFactory jobFactory = new WindsorJobFactory(container);
container.Register();
container.RegisterJobs(jobFactory);
I am not able to figure out what's wrong. I searched for the solution and found many links but it didn't help because all of them show only one level of dependency. What if the dependent class is dependent on another class?
You can find my demo project here:DemoProject
Some links I checked
Quartz .net Windsor Facility
Thank You
I have an MVC application that uses Entity Framework. I am using a repository, unit of work and unity as dependency injection.
The problem I have is that I have different authentication types, and each type I want a different class, so I decided to use the Strategy pattern
public interface IAuthStrategy
{
OperationResponse<AuthenticationMechanismDTO> GetAuthenticationMechanism(string userName);
}
public class AuthStrategy
{
readonly IAuthStrategy _authStrategy;
public AuthStrategy(IAuthStrategy authStrategy)
{
this._authStrategy = authStrategy;
}
public OperationResponse<AuthenticationMechanismDTO> GetAuthenticationMechanism(string userName)
{
return _authStrategy.GetAuthenticationMechanism(userName);
}
}
public class UserNamePasswordMechanism : IAuthStrategy
{
private IInstitutionRepository _institutionRepository;
public UserNamePasswordMechanism(IInstitutionRepository institutionRepository)
{
this._institutionRepository = institutionRepository;
}
public OperationResponse<AuthenticationMechanismDTO> GetAuthenticationMechanism(string userName)
{
throw new NotImplementedException();
}
}
My problem is that I am injecting IAuthStrategy into the controller, and it gives me an error, because instead of implementing IAuthStrategy, I am passing that to AuthStrategy constructor, as you can see that in my code.
How can I fix this error?
Here is my controller
public class EmployeeController : ApiController
{
private IAuthStrategy _auth;
public EmployeeController(IAuthStrategy auth)
{
this._employeeBL = employeeBL;
this._auth = auth;
}}
}
Here is unity config where i am registering my types
public class UnityConfig
{
#region Unity Container
private static Lazy<IUnityContainer> container = new Lazy<IUnityContainer>(() =>
{
var container = new UnityContainer();
RegisterTypes(container);
return container;
});
/// <summary>
/// Gets the configured Unity container.
/// </summary>
public static IUnityContainer GetConfiguredContainer()
{
return container.Value;
}
#endregion
/// <summary>Registers the type mappings with the Unity container.</summary>
/// <param name="container">The unity container to configure.</param>
/// <remarks>There is no need to register concrete types such as controllers or API controllers (unless you want to
/// change the defaults), as Unity allows resolving a concrete type even if it was not previously registered.</remarks>
public static void RegisterTypes(IUnityContainer container)
{
// NOTE: To load from web.config uncomment the line below. Make sure to add a Microsoft.Practices.Unity.Configuration to the using statements.
// container.LoadConfiguration();
// TODO: Register your types here
container.RegisterType<IInstitutionRepository, InstitutionRepository>();
container.RegisterType<IAuthStrategy, AuthStrategy>();
GlobalConfiguration.Configuration.DependencyResolver = new UnityDependencyResolver(container);
}
}
Your unit registrations and classes look a little off.
From what I can gather, this is what you really want to do.
Setup a factory that will determine at runtime which IAuthStrategy should be used:
public interface IAuthStrategyFactory
{
IAuthStrategy GetAuthStrategy();
}
public class AuthStrategyFactory : IAuthStrategyFactory
{
readonly IAuthStrategy _authStrategy;
public AuthStrategy(...)
{
//determine the concrete implementation of IAuthStrategy that you need
//This might be injected as well by passing
//in an IAuthStrategy and registering the correct one via unity at startup.
_authStrategy = SomeCallToDetermineWhichOne();
}
public IAuthStrategy GetAuthStrategy()
{
return _authStrategy;
}
}
This is your existing AuthStrategy:
public interface IAuthStrategy
{
OperationResponse<AuthenticationMechanismDTO> GetAuthenticationMechanism(string userName);
}
public class UserNamePasswordMechanism : IAuthStrategy
{
private IInstitutionRepository _institutionRepository;
public UserNamePasswordMechanism(IInstitutionRepository institutionRepository)
{
this._institutionRepository = institutionRepository;
}
public OperationResponse<AuthenticationMechanismDTO> GetAuthenticationMechanism(string userName)
{
throw new NotImplementedException();
}
}
Register the factory with unity:
container.RegisterType<IAuthStrategyFactory, AuthStrategyFactory>();
In your controller:
public class EmployeeController : ApiController
{
private IAuthStrategy _auth;
public EmployeeController(IAuthStrategyFactory authFactory)
{
this._employeeBL = employeeBL;
this._auth = authFactory.GetAuthStrategy();
}
}
Actually i missed implemented IAuthStrategyFactory on AuthStrategyFactory, once i implemented and register in unity container that worked.
Thanks
I have WebApi project with ODataController and I'm trying to inject some dependency into MyController. I was following this blogpost by Mark Seemann.
Consider code below.
Problem is, that when is MyController creating, I got exception inside WindsorCompositionRoot Create method on this line,
var controller = (IHttpController)this.container.Resolve(controllerType);
An exception of type 'Castle.MicroKernel.ComponentNotFoundException'
occurred in Castle.Windsor.dll but was not handled in user code
Additional information: No component for supporting the service
System.Web.OData.MetadataController was found
Any idea how to fix this?
Thank you.
My controller:
public class MyController : ODataController
{
private readonly DataLayer _db;
public PrepravyController(DataLayer db)
{
_db = db;
}
}
CompositonRoot:
public class WindsorCompositionRoot : IHttpControllerActivator
{
private readonly IWindsorContainer container;
public WindsorCompositionRoot(IWindsorContainer container)
{
this.container = container;
}
public IHttpController Create(
HttpRequestMessage request,
HttpControllerDescriptor controllerDescriptor,
Type controllerType)
{
var controller =
(IHttpController)this.container.Resolve(controllerType);
request.RegisterForDispose(
new Release(
() => this.container.Release(controller)));
return controller;
}
private class Release : IDisposable
{
private readonly Action release;
public Release(Action release)
{
this.release = release;
}
public void Dispose()
{
this.release();
}
}
}
Global asax:
var container = new WindsorContainer();
container.Install(new RepositoriesInstaller());
GlobalConfiguration.Configuration.Services.Replace(typeof(IHttpControllerActivator), new WindsorCompositionRoot(container));
GlobalConfiguration.Configure(WebApiConfig.Register);
Make sure you're registering all your controllers with the container:
public class ControllerInstaller : IWindsorInstaller
{
public void Install(IWindsorContainer container, IConfigurationStore store)
{
container.Register(Classes.FromThisAssembly().BasedOn<IController>().LifestylePerWebRequest())
.Register(Classes.FromThisAssembly().BasedOn<ApiController>().LifestylePerWebRequest());
}
}
Windsor uses installers to encapsulate and partition registration logic. It also includes a helper called FromAssembly, so you don't need to manually instantiate all your installers:
_container = new WindsorContainer();
_container.Install(FromAssembly.This());