Given That
Component.For<IService>().ImplementedBy<SecretService>().Named("secretService")
Component.For<IService>().ImplementedBy<PublicService>().Named("publicService")
And
class Foo{
public Foo(IService publicService){ ...... }
}
And
class Bar{
public Bar(IService secretService){ ...... }
}
Then how can i achieve the following
Foo and Bar should get instances of publicService and secretService respectively, entirely based on name of their constructor parameters.
I have now made it to work using a custom SubDependencyResolver, i added this to the container and now it injects the implementation by name
public class ByParameterNameResolver : ISubDependencyResolver
{
private readonly IKernel kernel;
public ByParameterNameResolver(IKernel kernel)
{
this.kernel = kernel;
}
public virtual bool CanResolve(CreationContext context, ISubDependencyResolver contextHandlerResolver, ComponentModel model, DependencyModel dependency)
{
if (dependency.TargetItemType == null)
return false;
if (string.IsNullOrWhiteSpace(dependency.DependencyKey))
return false;
return kernel.HasComponent(dependency.DependencyKey);
}
public virtual object Resolve(CreationContext context, ISubDependencyResolver contextHandlerResolver, ComponentModel model, DependencyModel dependency)
{
return kernel.Resolve(dependency.DependencyKey, dependency.TargetItemType);
}
}
Related
I am struggling to register with Autofac a hierarchy of classes and interfaces.
I have an interface IMyService defined as below:
public interface IMyService
{
void DoMyService();
}
And I have two abstract classes with implement this interface and called MyServiceA, and MyServiceB:
public abstract class MyServiceA : IMyService
{
public abstract DoMyService();
}
public abstract class MyServiceB : IMyService
{
public abstract DoMyService();
}
Moreover I have a second-level hierarchy for each of the two aforementioned services: MyServiceA1, MyServiceA2, MyServiceB1 and MyServiceB2:
public class MyServiceA1 : MyServiceA
{
public MyServiceA1() : base() {}
public void DoMyService()
{
// Implementation goes here
}
}
public class MyServiceA2 : MyServiceA
{
public MyServiceA2() : base() {}
public void DoMyService()
{
// Implementation goes here
}
}
public class MyServiceB1 : MyServiceB
{
public MyServiceB1() : base() {}
public void DoMyService()
{
// Implementation goes here
}
}
public class MyServiceB2 : MyServiceB
{
public MyServiceB2() : base() {}
public void DoMyService()
{
// Implementation goes here
}
}
I have in input two enums FirstEnum and SecondEnum used to select which of the four concrete types to instantiate:
public enum FirstEnum
{
SvcA,
SvcB
}
public enum SecondEnum
{
Svc1,
Svc2
}
I want to register IMyService and by providing two enums, It will automatically instantiate the good concrete type.
For instance, if I want to resolve an IMyService and I provide FirstEnum.SvcB and SecondEnum.Svc2, it should instantiate the concrete type MyServiceB2 class. Moreover this hierarchy might be updated by adding some other concrete types etc, so I need a generic way of doing it
Does anyone have a clue to help me?
Thanks
If you want to create a specific service dynamically depending on a set of parameters, this is a good use case for an abstract factory:
public interface IMyServiceFactory
{
IMyService Create(FirstEnum e1, SecondEnum e2);
}
public class MyServiceFactory : IMyServiceFactory
{
private readonly ILifetimeScope scope;
public MyServiceFactory(ILifetimeScope scope)
{
if (scope == null)
throw new ArgumentNullException("scope");
this.scope = scope;
}
public IMyService Create(FirstEnum e1, SecondEnum e2)
{
if (e1 == FirstEnum.SvcA)
{
if (e2 == SecondEnum.Svc1)
{
return scope.Resolve<MyServiceA1>();
}
else //svc2
{
return scope.Resolve<MyServiceA2>();
}
}
else //B
{
if (e2 == SecondEnum.Svc1)
{
return scope.Resolve<MyServiceB1>();
}
else //svc2
{
return scope.Resolve<MyServiceB2>();
}
}
}
}
And now your consumer need to get the factory injected instead of the service:
public class MyServiceConsumer
{
private readonly IMyServiceFactory factory;
public MyServiceConsumer(IMyServiceFactory factory)
{
this.factory = factory;
}
public void Do()
{
//var service = this.factory.Create
}
}
Registration :
Autofac.ContainerBuilder builder = new Autofac.ContainerBuilder();
builder.RegisterType<MyServiceA1>().AsSelf().AsImplementedInterfaces();
builder.RegisterType<MyServiceA2>().AsSelf().AsImplementedInterfaces();
builder.RegisterType<MyServiceB1>().AsSelf().AsImplementedInterfaces();
builder.RegisterType<MyServiceB2>().AsSelf().AsImplementedInterfaces();
builder.RegisterType<MyServiceFactory>().As<IMyServiceFactory>();
builder.RegisterType<MyServiceConsumer>();
//and quick test resolve
var container = builder.Build();
var test = container.Resolve<MyServiceConsumer>();
I am facing issue of mapping. My solution is as below.
I have two projects
1. Azure Function (v1) project with Framework: .Net Framework 4.7.2
2. Class Library with Framework: .Net Framework 4.7.2
In 1st project i have an azure function which is triggering using Queue and call my function BeginBackup(CancellationToken token, DateTime.Now()) which exist in my concreate class.
I am calling my function as below from my Azure function.
DependencyContext.Instance.Locator.GetInstance<IBackupTableStorageService>().BeginBackup(cancellationToken, SystemTime.UtcNow());
My DependencyContext.cs class is below.
using ClassLibrary1.BackupTableStorage;
using CommonServiceLocator;
using StructureMap;
using System;
using System.Collections.Generic;
namespace AzureFunctionsProject.Functions
{
public interface IDependencyContext
{
IServiceLocator Locator { get; }
}
public class DependencyContext : IDependencyContext
{
private static volatile IDependencyContext _instance;
private static readonly object SyncRoot = new Object();
public static IDependencyContext Instance
{
get
{
if (_instance == null)
{
lock (SyncRoot)
{
if (_instance == null)
{
_instance = new DependencyContext();
}
}
}
return _instance;
}
set => _instance = value;
}
public IServiceLocator Locator { get; private set; }
public DependencyContext()
{
Build();
}
private void Build()
{
var registry = new Registry();//Registry is the class belongs to StructureMap.
var container = new Container();
var serviceLocatorProvider = new StructureMapServiceLocator(container);
ServiceLocator.SetLocatorProvider(() => serviceLocatorProvider);
Locator = serviceLocatorProvider;
// register the container itself
registry.For<IServiceLocator>().Use(ServiceLocator.Current);
// Apply the registry to the container
container.Configure(x =>
{
x.AddRegistry<Domain.Registry>();
x.AddRegistry(registry);
});
}
}
public class StructureMapServiceLocator : ServiceLocatorImplBase
{
private IContainer Container { get; set; }
public StructureMapServiceLocator(IContainer container)
{
Container = container;
}
protected override object DoGetInstance(Type serviceType, string key)
{
if (string.IsNullOrEmpty(key))
{
return Container.GetInstance(serviceType);
}
return Container.GetInstance(serviceType, key);
}
protected override IEnumerable<object> DoGetAllInstances(Type serviceType)
{
foreach (object obj in Container.GetAllInstances(serviceType))
{
yield return obj;
}
}
}
}
I have another Registery class which i have created which have mapping of my interface with my concrete class.
Registery.cs file is below.
namespace ClassLibrary1.Domain
{
public class Registry: StructureMap.Registry
{
public Registry()
{
// The Localization Service needs to be passed a function to record exceptions
For<ILocalizationService>().Use<LocalizationService>()
.Ctor<LocalizationService.LogException>().Is(context => CreateExceptionLogger(context));
For<ICloudStorageWrapper>().Use<CloudStorageWrapper>();
For<IBackupTableStorageService>().Use<BackupTableStorageService>();
}
private LocalizationService.LogException CreateExceptionLogger(IContext context)
{
return (ex, c, m) =>
{
var logger = context.GetInstance<ILogicalOperationsLogger>();
logger.ErrorException(m, ex);
};
}
}
}
Like wise i have my Interface and respected to concreate class which has the definition of my method BeginBackup(CancellationToken token, DateTime.Now());
I am getting exception in DoGetInstance method in DependencyContext.cs class.
I am new in IoC and dependency injection, please let me know what i am doing wrong, if anything required to make question more clear please let me know.
Try to move the registration for IServiceLocator into the configure action. You can also remove the Registry-object you created:
private void Build()
{
var container = new Container();
var serviceLocatorProvider = new StructureMapServiceLocator(container);
ServiceLocator.SetLocatorProvider(() => serviceLocatorProvider);
Locator = serviceLocatorProvider;
// Apply the registry to the container
container.Configure(x =>
{
// register the container itself
x.For<IServiceLocator>().Use(serviceLocatorProvider);
x.AddRegistry<Domain.Registry>();
});
}
I've been at it for days, but I can't get Unity to inject anything with RegisterType<> into my Controller. I'm using Web Api 2, in Visual Studio 2015, with Unity 4. Whenever I try to inject IUnitOfWork or IRFContext, I get "message": "An error occurred when trying to create a controller of type 'ClPlayersController'. Make sure that the controller has a parameterless public constructor.".
I'm using the Unity.AspNet.WebApi to bootstrapp into WebApi. Below is my UnityWebApiActivator
[assembly: WebActivatorEx.PreApplicationStartMethod(typeof(mycompany.project.api.UnityWebApiActivator), "Start")]
[assembly: WebActivatorEx.ApplicationShutdownMethod(typeof(mycompany.project.api.UnityWebApiActivator), "Shutdown")]
namespace mycompany.project.api
{
public static class UnityWebApiActivator
{
public static void Start()
{
var resolver = new UnityDependencyResolver(UnityConfig.GetConfiguredContainer());
GlobalConfiguration.Configuration.DependencyResolver = resolver;
}
public static void Shutdown()
{
var container = UnityConfig.GetConfiguredContainer();
container.Dispose();
}
}
}
I'm using a Start.cs due to Owin.
[assembly: OwinStartup(typeof(mycompany.project.api.Startup))]
namespace mycompany.project.api
{
public class Startup
{
public void Configuration(IAppBuilder app)
{
HttpConfiguration config = new HttpConfiguration();
ConfigureOAuth(app);
config.DependencyResolver = new UnityDependencyResolver(UnityConfig.GetConfiguredContainer());
WebApiConfig.Register(config);
app.UseCors(Microsoft.Owin.Cors.CorsOptions.AllowAll);
app.UseWebApi(config);
}
public void ConfigureOAuth(IAppBuilder app)
{
OAuthAuthorizationServerOptions OAuthServerOptions = new OAuthAuthorizationServerOptions()
{
AllowInsecureHttp = true,
TokenEndpointPath = new PathString("/token"),
AccessTokenExpireTimeSpan = TimeSpan.FromDays(1),
Provider = new SimpleAuthorizationServerProvider(),
RefreshTokenProvider = new SimpleRefreshTokenProvider()
};
// Token Generation
app.UseOAuthAuthorizationServer(OAuthServerOptions);
app.UseOAuthBearerAuthentication(new OAuthBearerAuthenticationOptions());
}
}
}
My WebApiConfig.cs is below:
namespace mycompany.project.api
{
public static class WebApiConfig
{
public static void Register(HttpConfiguration config)
{
log4net.Config.XmlConfigurator.Configure();
config.MapHttpAttributeRoutes();
config.EnableSystemDiagnosticsTracing();
config.Services.Add(typeof(IExceptionLogger),
new SimpleExceptionLogger(new LogManagerAdapter()));
config.Services.Replace(typeof(IExceptionHandler), new GlobalExceptionHandler());
}
}
}
My UnityConfig.cs is below
namespace mycompany.project.api
{
public class UnityConfig
{
#region Unity Container
private static Lazy<IUnityContainer> container = new Lazy<IUnityContainer>(() =>
{
var container = new UnityContainer();
RegisterTypes(container);
return container;
});
public static IUnityContainer GetConfiguredContainer()
{
return container.Value;
}
#endregion
public static void RegisterTypes(IUnityContainer container)
{
var config = new MapperConfiguration(cfg =>
{
//AutoMapper bindings
});
container.RegisterInstance<IMapper>(config.CreateMapper());
container.RegisterType<IRFContext, RFContext>(new PerThreadLifetimeManager());
container.RegisterType<IUnitOfWork, UnitOfWork>();
XmlConfigurator.Configure();
var logManager = new LogManagerAdapter();
container.RegisterInstance<ILogManager>(logManager);
}
}
}
All that I have in my Global.asax is below:
public class WebApiApplication : System.Web.HttpApplication
{
protected void Application_Error()
{
var exception = Server.GetLastError();
if (exception != null)
{
var log = new LogManagerAdapter().GetLog(typeof(WebApiApplication));
log.Error("Unhandled exception.", exception);
}
}
}
If my Controller is like this, it works fine:
public class ClPlayersController : ApiController
{
private readonly IMapper mapper;
public ClPlayersController(IMapper _mapper, IUnityContainer container)
{
mapper = _mapper;
}
But placing IUnitOfWork, like below, or the IRFContext, I get the error:
private readonly IMapper mapper;
private readonly IUnitOfWork unitOfWork;
public ClPlayersController(IMapper _mapper, IUnityContainer container, IUnitOfWork _unitOfWork)
{
mapper = _mapper;
unitOfWork = _unitOfWork;
}
I can't find, for the life of me, what I'm doing wrong. If I loop through the container.Registrations on the constructor, I find the mappings, but they refuse to get injected. Any hints?
EDIT
Below is the code for UnitOfWork and RFContext
namespace mycompany.project.data.configuracao
{
public class UnitOfWork : IUnitOfWork
{
private readonly IRFContext _rfContext;
private bool _disposed = false;
public UnitOfWork(IRFContext rfContext)
{
_rfContext = rfContext;
}
public void Commit()
{
if (_disposed)
{
throw new ObjectDisposedException(this.GetType().FullName);
}
_rfContext.SaveChanges();
}
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
protected virtual void Dispose(bool disposing)
{
if (_disposed) return;
if (disposing && _rfContext != null)
{
_rfContext.Dispose();
}
_disposed = true;
}
}
}
and
namespace mycompany.project.data.configuracao
{
public interface IUnitOfWork : IDisposable
{
void Commit();
}
}
and RFContext is a basic POCO generated DBContext
namespace mycompany.project.data.configuracao
{
using System.Linq;
public class RFContext : System.Data.Entity.DbContext, IRFContext
{
public System.Data.Entity.DbSet<ClGrupoEconomico> ClGrupoEconomicoes { get; set; }
//all my DbSets
public System.Data.Entity.DbSet<SpTipoLog> SpTipoLogs { get; set; }
static RFContext()
{
System.Data.Entity.Database.SetInitializer<RFContext>(null);
}
public RFContext()
: base("Name=RFContext")
{
}
public RFContext(string connectionString)
: base(connectionString)
{
}
public RFContext(string connectionString, System.Data.Entity.Infrastructure.DbCompiledModel model)
: base(connectionString, model)
{
}
public RFContext(System.Data.Common.DbConnection existingConnection, bool contextOwnsConnection)
: base(existingConnection, contextOwnsConnection)
{
}
public RFContext(System.Data.Common.DbConnection existingConnection, System.Data.Entity.Infrastructure.DbCompiledModel model, bool contextOwnsConnection)
: base(existingConnection, model, contextOwnsConnection)
{
}
protected override void Dispose(bool disposing)
{
base.Dispose(disposing);
}
protected override void OnModelCreating(System.Data.Entity.DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Configurations.Add(new ClGrupoEconomicoConfiguration());
//all my Configuration classes
modelBuilder.Configurations.Add(new SpTipoLogConfiguration());
}
public static System.Data.Entity.DbModelBuilder CreateModel(System.Data.Entity.DbModelBuilder modelBuilder, string schema)
{
modelBuilder.Configurations.Add(new ClGrupoEconomicoConfiguration(schema));
//all my configuration classes
modelBuilder.Configurations.Add(new SpTipoLogConfiguration(schema));
return modelBuilder;
}
}
}
Unfortunately the exception you are seeing can occur for several reasons. One of them is when Unity cannot resolve one or more of your injections.
An error occurred when trying to create a controller of type
'FooController'. Make sure that the controller has a parameterless
public constructor.
So, based on the information in your question your setup is apparently correct, since IMapper can be injected. Therefore I guess that UnitOfWork and RFContext have dependencies that Unity cannot resolve. Maybe a repository?
UPDATE:
The problem here is that your RFContext has several constructors.
https://msdn.microsoft.com/en-us/library/cc440940.aspx#cnstrctinj_multiple
When a target class contains more than one constructor with the same
number of parameters, you must apply the InjectionConstructor
attribute to the constructor that the Unity container will use to
indicate which constructor the container should use. As with automatic
constructor injection, you can specify the constructor parameters as a
concrete type, or you can specify an interface or base class for which
the Unity container contains a registered mapping.
In this case Unity doesn't know how to resolve your RFContext, and will try to use the constructor with the most parameters. You can solve it by using
container.RegisterType<IRFContext, RFContext>(new InjectionConstructor());
I am working on an ASP.NET WebAPI using OWIN. To manage the instances of DBContext (Entity Framework), I try to use Ninject. However, when I call a controller, the programm returns an error:
The controller cannot be created, missing constructor.
Could you tell me what is going wrong here?
My Controller Class:
public class Testcontroller
{
private IApplicationDbContext _context;
public Testcontroller(IApplicationDbContext context)
{
_context = context;
}
}
This is the Ninject-File:
public static class NinjectWebCommon
{
private static readonly Bootstrapper bootstrapper = new Bootstrapper();
public static void Start()
{
DynamicModuleUtility.RegisterModule(typeof(OnePerRequestHttpModule));
DynamicModuleUtility.RegisterModule(typeof(NinjectHttpModule));
bootstrapper.Initialize(CreateKernel);
}
public static void Stop()
{
bootstrapper.ShutDown();
}
private static IKernel CreateKernel()
{
var kernel = new StandardKernel();
try
{
kernel.Bind<Func<IKernel>>().ToMethod(ctx => () => new Bootstrapper().Kernel);
kernel.Bind<IHttpModule>().To<HttpApplicationInitializationHttpModule>();
kernel.Bind<IApplicationDbContext>().To<ApplicationDbContext>();
GlobalConfiguration.Configuration.DependencyResolver = new NinjectDependencyResolver(kernel);
RegisterServices(kernel);
return kernel;
}
catch
{
kernel.Dispose();
throw;
}
}
private static void RegisterServices(IKernel kernel)
{
}
}
Ninject Dependency Scope:
public class NinjectDependencyScope : IDependencyScope
{
IResolutionRoot resolver;
public NinjectDependencyScope(IResolutionRoot resolver)
{
this.resolver = resolver;
}
public object GetService(Type serviceType)
{
if (resolver == null)
throw new ObjectDisposedException("this", "This scope has been disposed");
return resolver.TryGet(serviceType);
}
public System.Collections.Generic.IEnumerable<object> GetServices(Type serviceType)
{
if (resolver == null)
throw new ObjectDisposedException("this", "This scope has been disposed");
return resolver.GetAll(serviceType);
}
public void Dispose()
{
IDisposable disposable = resolver as IDisposable;
if (disposable != null)
disposable.Dispose();
resolver = null;
}
}
// This class is the resolver, but it is also the global scope
// so we derive from NinjectScope.
public class NinjectDependencyResolver : NinjectDependencyScope, IDependencyResolver
{
IKernel kernel;
public NinjectDependencyResolver(IKernel kernel) : base(kernel)
{
this.kernel = kernel;
}
public IDependencyScope BeginScope()
{
return new NinjectDependencyScope(kernel.BeginBlock());
}
}
The Entity Framework DbContext-Class:
public class ApplicationDbContext : IdentityDbContext<ApplicationUser>, IApplicationDbContext
{
public ApplicationDbContext()
: base("DefaultConnection", throwIfV1Schema: false)
{
Configuration.ProxyCreationEnabled = false;
Configuration.LazyLoadingEnabled = false;
}
public virtual DbSet<Models.Team> Teams { get; set; }
public static ApplicationDbContext Create()
{
return new ApplicationDbContext();
}
}
public interface IApplicationDbContext
{
DbSet<Models.Team> Teams { get; set; }
int SaveChanges();
Task<int> SaveChangesAsync(CancellationToken cancellationToken);
}
I tried to follow this tutorial: http://www.peterprovost.org/blog/2012/06/19/adding-ninject-to-web-api
What have I done wrong here?
Thanks in advance!
Unless there was a serious omission in you controller code, your controller is not inheriting from ApiController, as is expected with Web Api
public class TestController : ApiController {
private IApplicationDbContext _context;
public Testcontroller(IApplicationDbContext context) {
_context = context;
}
}
UPDATE
I tried to set up everything from scratch using this: http://www.alexzaitzev.pro/2014/11/webapi2-owin-and-ninject.html
For some reason, it now works out perfectly fine.
Thank you for your support!
We are using Caliburn Micro for the first time.
We have a AppBootstrapper inherited from ShellViewModel.
Situvation is that VieModels should have the same instance unless it is reset.
we are able to achieve shared or not shared everytime, but releasing the export whenever needed is still a mystery.
public class AppBootstrapper : Bootstrapper<ShellViewModel>
{
private static CompositionContainer _container;
protected override void Configure()
{
try
{
_container = new CompositionContainer(
new AggregateCatalog(AssemblySource.Instance.Select(x => new AssemblyCatalog(x))));
var batch = new CompositionBatch();
batch.AddExportedValue<IWindowManager>(new WindowManager());
batch.AddExportedValue<IEventAggregator>(new EventAggregator());
batch.AddExportedValue(_container);
StyleManager.ApplicationTheme = ThemeManager.FromName("Summer");
_container.Compose(batch);
}
catch (Exception exception)
{
}
}
public static void ReleaseAll()
{
}
protected override object GetInstance(Type serviceType, string key)
{
try
{
var contract = string.IsNullOrEmpty(key) ? AttributedModelServices.GetContractName(serviceType) : key;
var exports = _container.GetExportedValues<object>(contract);
if (exports.Any())
return exports.First();
throw new Exception(string.Format("Could not locate any instances of contract {0}.", contract));
}
catch (ReflectionTypeLoadException ex)
{
foreach (Exception inner in ex.LoaderExceptions)
{
// write details of "inner", in particular inner.Message
}
return null;
}
}
protected override IEnumerable<object> GetAllInstances(Type serviceType)
{
try
{
return _container.GetExportedValues<object>(AttributedModelServices.GetContractName(serviceType));
}
catch (Exception exception)
{
return null;
}
}
protected override void BuildUp(object instance)
{
_container.SatisfyImportsOnce(instance);
}
}
ShellViewModel
[Export(typeof(ShellViewModel))]
public sealed class ShellViewModel : Conductor<IScreen>.Collection.OneActive, IHandle<object>
{
[ImportingConstructor]
public ShellViewModel(CompositionContainer compositionContainer, IEventAggregator eventAggregator)
{
CompositionContainer = compositionContainer;
EventAggregator = eventAggregator;
eventAggregator.Subscribe(this);
Items.Add(compositionContainer.GetExportedValue<AViewModel>());
Items.Add(compositionContainer.GetExportedValue<BViewModel>());
ActivateItem(Items.Single(p => p.DisplayName == AppMessageType.A.ToString()));
}
public IEventAggregator EventAggregator { get; set; }
public CompositionContainer CompositionContainer { get; set; }
public void Handle(object message)
{
//throw new System.NotImplementedException();
}
public void B()
{
ActivateItem(Items.Single(p => p.DisplayName == AppMessageType.B.ToString()));
}
public void A()
{
ActivateItem(Items.Single(p => p.DisplayName == AppMessageType.A.ToString()));
}
public void RESET()
{
AppBootstrapper.ReleaseAll();
ActivateItem(Items.Single(p => p.DisplayName == AppMessageType.A.ToString()));
}
public enum AppMessageType
{
A,
B
}
}
AViewModel
[Export(typeof(AViewModel))]
public sealed class AViewModel : Conductor<IScreen>.Collection.OneActive, IHandle<object>
{
[ImportingConstructor]
public AViewModel(CompositionContainer compositionContainer, IEventAggregator eventAggregator)
{
DisplayName = ShellViewModel.AppMessageType.A.ToString();
CompositionContainer = compositionContainer;
EventAggregator = eventAggregator;
eventAggregator.Subscribe(this);
}
public IEventAggregator EventAggregator { get; set; }
public CompositionContainer CompositionContainer { get; set; }
public void Handle(object message)
{
//throw new System.NotImplementedException();
}
}
BViewModel
[Export(typeof(BViewModel))]
public sealed class BViewModel : Conductor<IScreen>.Collection.OneActive, IHandle<object>
{
[ImportingConstructor]
public BViewModel(CompositionContainer compositionContainer, IEventAggregator eventAggregator)
{
DisplayName = ShellViewModel.AppMessageType.B.ToString();
CompositionContainer = compositionContainer;
EventAggregator = eventAggregator;
eventAggregator.Subscribe(this);
}
public IEventAggregator EventAggregator { get; set; }
public CompositionContainer CompositionContainer { get; set; }
public void Handle(object message)
{
//throw new System.NotImplementedException();
}
}
Now AViewModel and BViewModel have single instance.
Whenever Release Button is clicked i want to have new instance of AViewModel and BViewModel.
Hoping to get a reply soon.
Regards,
Vivek
When working with an IoC container, the only part of your code that should take it as a dependency should be your composition root (i.e. your AppBootstrapper in this case). You shouldn't be injecting or referencing the container anywhere else in your code (except possibly factories).
If you want your ShellViewModel to control the lifetime of your child view models (A and B), then you should consider injecting view model factories into your ShellViewModel (via constructor injection if they are required dependencies).
Your AViewModelFactory would just have a single Create method that returns a new instance of AViewModel, likewise with the BViewModelFactory. You can simply new up your view models directly in the factories. If your view models have large dependency chains themselves, then you could consider adding a reference to your container in the factories, although preferably consider looking into the MEF ExportFactory<T> type.