Suppose I have a dependency that is registered as HttpRequestScoped so there is only one instance per request. How could I resolve a dependency of the same type outside of an HttpRequest?
For example:
// Global.asax.cs Registration
builder.Register(c => new MyDataContext(connString)).As<IDatabase>().HttpRequestScoped();
_containerProvider = new ContainerProvider(builder.Build());
// This event handler gets fired outside of a request
// when a cached item is removed from the cache.
public void CacheItemRemoved(string k, object v, CacheItemRemovedReason r)
{
// I'm trying to resolve like so, but this doesn't work...
var dataContext = _containerProvider.ApplicationContainer.Resolve<IDatabase>();
// Do stuff with data context.
}
The above code throws a DependencyResolutionException when it executes the CacheItemRemoved handler:
No scope matching the expression 'value(Autofac.Builder.RegistrationBuilder`3+<>c__DisplayClass0[MyApp.Core.Data.MyDataContext,Autofac.Builder.SimpleActivatorData,Autofac.Builder.SingleRegistrationStyle]).lifetimeScopeTag.Equals(scope.Tag)' is visible from the scope in which the instance was requested.
InstancePerLifetimeScope(), rather than HttpRequestScoped(), will give the result you need.
There is a caveat though - if IDatabase requires disposal, or depends on something that requires disposal, this won't happen if you resolve it from the ApplicationContainer. Better to do:
using (var cacheRemovalScope =
_containerProvider.ApplicationContainer.BeginLifetimeScope())
{
var dataContext = cacheRemovalScope.Resolve<IDatabase>();
// Do what y' gotta do...
}
Related
I've been assigned to upscale a project built by a former coworker. I'm not a .NET Core specialist, I understand most of it as is similar to any other language, but I'm having trouble understanding the Fluent configuration made at startup.
At the Startup.cs, there is this function declared:
public void Configure(IApplicationBuilder app)
At some point, there is an initialzation of a service that listens for something. I can manage that from the already initialized class/service, but I'd like to understand what is this:
app.UseRawRequestRequestBodyHandler(options => options
.Handlers
.AddRange(new[] {
new RawRequestHandler
{
ContentType = NotificationSubscriber.ContentType,
StartSegments = NotificationSubscriber.StartSegments,
Response = "[OK]",
Endpoint = new Uri(_configManager.Client.BaseAddress, "v1/payments").ToString(),
ModifyRequestBodyAsyncFunc = async (handler, context, bodyContent) =>
{
using (var scope = app.ApplicationServices.CreateScope())
{
var subscriber = scope.ServiceProvider
.GetRequiredService<INotificationSubscriber>();
await subscriber.QueueAndAkcknowledgeAsync(handler, context, bodyContent);
}
return bodyContent;
}
},
I'm having special trobule with the ModifyRequestBodyAsyncFunc function, that is declared (in the interface) like this:
public Func<RawRequestHandler, HttpContext, string, Task<string>> ModifyRequestBodyAsyncFunc { set; get; }
Also, I don't get how or where are initialized handler, context and bodyContent (RawRequestHandler handler, HttpContext context, string bodyContent as declared in the NotificationSubscriber class). I pressume these are loaded by Dependency Injection, but It would be different for other DI implementations I've seen.
Any help would be appreciated; also, I take reading recommendations.
Thank you very much!
I'm having special trobule with the ModifyRequestBodyAsyncFunc function
This is a special C# type, called a delegate. The delegate in question is a function that accepts RawRequestHeader, HttpContext, string and returns a Task<string>, which tells us that it's asynchronous.
Next, this is a syntax to create an anonymous async function and assign it to the delegate property:
/* SomeProp */ = async (handler, context, bodyContent) =>
{
// ...
return bodyContent;
}
Also, I don't get how or where are initialized handler, context and bodyContent
The .UseRawRequestRequestBodyHandler(...) registers a middleware which is basically a piece of code which runs for every request. So, somewhere inside that middleware, there is code that has access to said parameters and probably passes them like that:
// the params are not necessarily named exactly like this, only the types must match
string content = await rawRequestHeader.ModifyRequestBodyAsyncFunc(handler, context, bodyContent);
Notice the await keyword (we must await asynchronous functions) and also the fact that the delegate is invoked just like a normal method.
In my project I am trying to get a user based on it's email adress every second with the UserManager but when I do this I get the following error Cannot access a disposed object Object name: 'UserManager1, but this is when I do it inside of a Timer(). If I just do it once there is no problem, how can I fix this? This timer is inside a class that is being called by a SignalR Hub.
Code:
Timer = new System.Threading.Timer(async (e) =>
{
IEnumerable<Conversation> conversations = await _conversationsRepo.GetAllConversationsForUserEmailAsync(userMail);
List<TwilioConversation> twilioConversations = new List<TwilioConversation>();
foreach (Conversation conversation in conversations)
{
TwilioConversation twilioConversation = await _twilioService.GetConversation(conversation.TwilioConversationID);
twilioConversation.Messages = await _twilioService.GetMessagesForConversationAsync(conversation.TwilioConversationID);
twilioConversation.ParticipantNames = new List<string>();
List<TwilioParticipant> participants = await _twilioService.GetParticipantsForConversationAsync(conversation.TwilioConversationID);
foreach (TwilioParticipant participant in participants)
{
User user = await _userManager.FindByEmailAsync(participant.Email);
twilioConversation.ParticipantNames.Add(user.Name);
}
twilioConversations.Add(twilioConversation);
}
}, null, startTimeSpan, periodTimeSpan);
UserManager along with quite a few other types is a service that has a scoped lifetime. This means that they are only valid within the lifetime of a single request.
That also means that holding on to an instance for longer is not a safe thing to do. In this particular example, UserManager depends on the UserStore which has a dependency on a database connection – and those will definitely be closed when the request has been completed.
If you need to run something outside of the context of a request, for example in a background thread, or in your case in some timed execution, then you should create a service scope yourself and retrieve a fresh instance of the dependency you rely on.
To do that, inject a IServiceScopeFactory and then use that to create the scope within your timer code. This also applies to all other scoped dependencies, e.g. your repository which likely requires a database connection as well:
Timer = new System.Threading.Timer(async (e) =>
{
using (var scope = serviceScopeFactory.CreateScope())
{
var conversationsRepo = scope.ServiceProvider.GetService<ConversionsRepository>();
var userManager = scope.ServiceProvider.GetService<UserManager<User>>();
// do stuff
}
}, null, startTimeSpan, periodTimeSpan);
There’s something which I am doing that is working, but I think it can probably be done a lot better (and therefore, with more maintainability).
I am using Ninject to inject various things into a controller. The problem which I needed to solve is that the DbContext for each repository needed to be the same. That is, the same object in memory.
Whilst, the following code does achieve that, my Ninject common config file has started to get quite messy as I have to write similar code for each controller:
kernel.Bind<OrderController>().ToMethod(ctx =>
{
var sharedContext = ctx.Kernel.Get<TTSWebinarsContext>();
var userAccountService = kernel.Get<UserAccountService>();
ILogger logger = new Log4NetLogger(typeof(Nml.OrderController));
ILogger loggerForOrderManagementService = new Log4NetLogger(typeof(OrderManagementService));
var orderManagementService = new OrderManagementService(
new AffiliateRepository(sharedContext),
new RegTypeRepository(sharedContext),
new OrderRepository(sharedContext),
new RefDataRepository(),
new WebUserRepository(sharedContext),
new WebinarRepository(sharedContext),
loggerForOrderManagementService,
ttsConfig
);
var membershipService = new MembershipService(
new InstitutionRepository(sharedContext),
new RefDataRepository(),
new SamAuthenticationService(userAccountService),
userAccountService,
new WebUserRepository(sharedContext)
);
return new OrderController(membershipService, orderManagementService, kernel.Get<IStateService>(), logger);
}).InRequestScope();
Is there a neater way of doing this?
Edit
Tried the following code. As soon as I make a second request, an exception is chucked that the DbContext has already been disposed.
kernel.Bind<TTSWebinarsContext>().ToSelf().InRequestScope();
string baseUrl = HttpRuntime.AppDomainAppPath;
kernel.Bind<IStateService>().To<StateService>().InRequestScope();
kernel.Bind<IRefDataRepository>().To<RefDataRepository>().InRequestScope().WithConstructorArgument("context", kernel.Get<TTSWebinarsContext>());
var config = MembershipRebootConfig.Create(baseUrl, kernel.Get<IStateService>(), kernel.Get<IRefDataRepository>());
var ttsConfig = TtsConfig.Create(baseUrl);
kernel.Bind<MembershipRebootConfiguration>().ToConstant(config);
kernel.Bind<TtsConfiguration>().ToConstant(ttsConfig);
kernel.Bind<IAffiliateRepository>().To<AffiliateRepository>().InRequestScope().WithConstructorArgument("context", kernel.Get<TTSWebinarsContext>());
kernel.Bind<IWebinarRepository>().To<WebinarRepository>().InRequestScope().WithConstructorArgument("context", kernel.Get<TTSWebinarsContext>());
kernel.Bind<IWebUserRepository>().To<WebUserRepository>().InRequestScope().WithConstructorArgument("context", kernel.Get<TTSWebinarsContext>());
kernel.Bind<IOrderRepository>().To<OrderRepository>().InRequestScope().WithConstructorArgument("context", kernel.Get<TTSWebinarsContext>());
kernel.Bind<IInstitutionRepository>().To<InstitutionRepository>().WithConstructorArgument("context", kernel.Get<TTSWebinarsContext>());
kernel.Bind<IUserAccountRepository>().To<DefaultUserAccountRepository>().InRequestScope();
kernel.Bind<IRegTypeRepository>().To<RegTypeRepository>().InRequestScope().WithConstructorArgument("context", kernel.Get<TTSWebinarsContext>());
kernel.Bind<UserAccountService>().ToMethod(ctx =>
{
var userAccountService = new UserAccountService(config, ctx.Kernel.Get<IUserAccountRepository>());
return userAccountService;
});
kernel.Bind<IOrderManagementService>().To<OrderManagementService>().InRequestScope();
//RegisterControllers(kernel, ttsConfig);
kernel.Bind<AuthenticationService>().To<SamAuthenticationService>().InRequestScope();
kernel.Bind<IMembershipService>().To<MembershipService>().InRequestScope();
There's something about InRequestScope I'm misunderstanding.
Edit:
.InRequestScope() will ensure everything which gets injected that binding will receive exactly the same instance when during injection (creation) the HttpContext.Current is the same. That means when a client makes a request and the kernel is asked to provide instances with .InRequestScope(), it will return the same instance for the exact same request. Now when a client makes another request, another unique instance will be created.
When the request ends, ninject will dispose the instance in case it implements IDisposable.
However consider the following scenario:
public class A
{
private readonly DbContext dbContext;
public A(DbContext dbContext)
{
this.dbContext = dbContext;
}
}
and binding:
IBindingRoot.Bind<DbContext>().ToSelf().InRequestScope();
IBindingRoot.Bind<A>().ToSelf().InSingletonScope();
You got yourself a major problem. There's two scenarios how this can pan out:
You are trying to create an A outside of a request. It will fail. Instantiating the DbContext, ninject will look for HttpContext.Current - which is null at the time - and throw an Exception.
You are trying to create an A during a request. Instantiating will succeed. However, When you try to use some functionality of A (which is accessing DbContext in turn) after the request or during a new request, it will throw an ObjectDisposedException
To sum it up, an ObjectDisposedException when you access the DbContext can only be caused by two scenarios:
-you ar disposing the DbContext (or some component which in turn disposes the DbContext) before the request is over.
-you are keeping a reference to the DbContext (again, or to some component which in turn references the DbContext) across request boundaries.
That's it. Nothing complicated about this, but your object graph.
So what would help is drawing an object graph. Start from the root / request root. Then when you're done, start from the DbContext and check who's calling Dispose() on it. If there is no usage inside your code, it must be Ninject who's cleaning up when the request ends. That means, you need to check all references to the DbContext. Someone is keeping a reference across requests.
Original Answer:
You should look into scopes: https://github.com/ninject/ninject/wiki/Object-Scopes
Specifically, .InRequestScope() - or in case that is not appliccable to your problem - .InCallScope() should be interesting to you.
As you are already using .InRequestScope() for the original binding, i suggest that binding the shared context type also .InRequestScope() should be sufficient. It means every dependency of the OrderController will receive the same webinar context instance. Furthermore, if someone else in the same request wants to get a webinar context injected, he will also get the same instance.
You should look into scopes: https://github.com/ninject/ninject/wiki/Object-Scopes
Specifically, .InRequestScope() - or in case that is not appliccable to your problem - .InCallScope() should be interesting to you.
As you are already using .InRequestScope() for the original binding, i suggest that binding the shared context type also .InRequestScope() should be sufficient. It means every dependency of the OrderController will receive the same webinar context instance. Furthermore, if someone else in the same request wants to get a webinar context injected, he will also get the same instance.
I am trying to adapt the MvcSiteMapProvider to create the breadcrumb based on some Information stored in a database.
The answer in this post sounded promising so i implemented my own SiteMapNodeProvider. But then i didnt know how to wire things up so the newly implemented SiteMapNodeProvider is used instead of the static xml file ("Mvc.sitemap").
As i am using SimpleInjector in my project, i called the setup method in my already existent Injection-initialization code.
public static void Initialize()
{
Injection.Global = new Container();
InitializeContainer(Injection.Global);
Injection.Global.RegisterMvcControllers(Assembly.GetExecutingAssembly());
Injection.Global.RegisterMvcAttributeFilterProvider();
Injection.Global.Verify();
DependencyResolver.SetResolver(new SimpleInjectorDependencyResolver(Injection.Global));
}
private static void InitializeContainer(Container container)
{
// Setup configuration of DI
MvcSiteMapProviderContainerInitializer.SetUp(container);
//... register some other stuff for my project here ...
}
The MvcSiteMapProviderContainerInitializer class got created by the package: 'Mvcsitemapprovider.mvc4.di.simpleinjector/4.4.5'
Does anybody know what to do to make my project use the newly created SiteMapNodeProvider?
I couldnt find any documentation about this in the official docu...
edit: i tried what you suggested (even removed the old DI stuff and only used the one from the nuget-package) but still i am getting errors...
here is what i have in my MvcSiteMapProviderContainerInitializer
public static void SetUp(Container container)
{
bool securityTrimmingEnabled = false;
bool enableLocalization = true;
string absoluteFileName = HostingEnvironment.MapPath("~/Mvc.sitemap");
TimeSpan absoluteCacheExpiration = TimeSpan.FromMinutes(5);
string[] includeAssembliesForScan = new string[] { "testsitemap" };
// Extension to allow resolution of arrays by GetAllInstances (natively based on IEnumerable).
// source from: https://simpleinjector.codeplex.com/wikipage?title=CollectionRegistrationExtensions
AllowToResolveArraysAndLists(container);
var currentAssembly = typeof(MvcSiteMapProviderContainerInitializer).Assembly;
var siteMapProviderAssembly = typeof(SiteMaps).Assembly;
var allAssemblies = new Assembly[] { currentAssembly, siteMapProviderAssembly };
var excludeTypes = new Type[]
{
typeof (SiteMapNodeVisibilityProviderStrategy),
typeof (SiteMapXmlReservedAttributeNameProvider),
typeof (SiteMapBuilderSetStrategy),
typeof (ControllerTypeResolverFactory),
// Added 2013-06-28 by eric-b to avoid default singleton registration:
typeof(XmlSiteMapController),
// Added 2013-06-28 by eric-b for SimpleInjector.Verify method:
typeof(PreservedRouteParameterCollection),
typeof(MvcResolver),
typeof(MvcSiteMapProvider.SiteMap),
typeof(MetaRobotsValueCollection),
typeof(RoleCollection),
typeof(SiteMapPluginProvider),
typeof(ControllerTypeResolver),
typeof(RouteValueDictionary),
typeof(AttributeDictionary)
,typeof(SiteMapNodeCreator)
};
var multipleImplementationTypes = new Type[]
{
typeof (ISiteMapNodeUrlResolver),
typeof (ISiteMapNodeVisibilityProvider),
typeof (IDynamicNodeProvider)
};
// Single implementations of interface with matching name (minus the "I").
CommonConventions.RegisterDefaultConventions(
(interfaceType, implementationType) => container.RegisterSingle(interfaceType, implementationType),
new Assembly[] { siteMapProviderAssembly },
allAssemblies,
excludeTypes,
string.Empty);
// Multiple implementations of strategy based extension points
CommonConventions.RegisterAllImplementationsOfInterfaceSingle(
(interfaceType, implementationTypes) => container.RegisterAll(interfaceType, implementationTypes),
multipleImplementationTypes,
allAssemblies,
new Type[0],
"^Composite");
container.Register<XmlSiteMapController>();
// Visibility Providers
container.RegisterSingle<ISiteMapNodeVisibilityProviderStrategy>(() =>
new SiteMapNodeVisibilityProviderStrategy(
container.GetAllInstances
<ISiteMapNodeVisibilityProvider>().
ToArray(), string.Empty));
// Pass in the global controllerBuilder reference
container.RegisterSingle<ControllerBuilder>(() => ControllerBuilder.Current);
container.RegisterSingle<IControllerBuilder, ControllerBuilderAdaptor>();
container.RegisterSingle<IBuildManager, BuildManagerAdaptor>();
container.RegisterSingle<IControllerTypeResolverFactory>(() =>
new ControllerTypeResolverFactory(new string[0],
container.GetInstance
<IControllerBuilder
>(),
container.GetInstance
<IBuildManager>()));
// Configure Security
container.RegisterAll<IAclModule>(typeof(AuthorizeAttributeAclModule), typeof(XmlRolesAclModule));
container.RegisterSingle<IAclModule>(() => new CompositeAclModule(container.GetAllInstances<IAclModule>().ToArray()));
// Setup cache
container.RegisterSingle<System.Runtime.Caching.ObjectCache>(() => System.Runtime.Caching.MemoryCache.Default);
container.RegisterSingleOpenGeneric(typeof(ICacheProvider<>), typeof(RuntimeCacheProvider<>));
container.RegisterSingle<ICacheDependency>(() => new RuntimeFileCacheDependency(absoluteFileName));
container.RegisterSingle<ICacheDetails>(() => new CacheDetails(absoluteCacheExpiration, TimeSpan.MinValue, container.GetInstance<ICacheDependency>()));
// Configure the visitors
container.RegisterSingle<ISiteMapNodeVisitor, UrlResolvingSiteMapNodeVisitor>();
// Prepare for the sitemap node providers
container.RegisterSingle<ISiteMapXmlReservedAttributeNameProvider>(
() => new SiteMapXmlReservedAttributeNameProvider(new string[0]));
container.RegisterSingle<IXmlSource>(() => new FileXmlSource(absoluteFileName));
// Register the sitemap node providers
container.RegisterSingle<XmlSiteMapNodeProvider>(() => container.GetInstance<XmlSiteMapNodeProviderFactory>()
.Create(container.GetInstance<IXmlSource>()));
container.RegisterSingle<ReflectionSiteMapNodeProvider>(() => container.GetInstance<ReflectionSiteMapNodeProviderFactory>()
.Create(includeAssembliesForScan));
// Register your custom sitemap node provider
container.RegisterSingle<ISiteMapNodeProvider, CustomSiteMapNodeProvider>();
// Register the collection of sitemap node providers (including the custom one)
container.RegisterSingle<ISiteMapBuilder>(() => container.GetInstance<SiteMapBuilderFactory>()
.Create(new CompositeSiteMapNodeProvider(
container.GetInstance<XmlSiteMapNodeProvider>(),
container.GetInstance<ReflectionSiteMapNodeProvider>(),
container.GetInstance<CustomSiteMapNodeProvider>())));
container.RegisterAll<ISiteMapBuilderSet>(ResolveISiteMapBuilderSets(container, securityTrimmingEnabled, enableLocalization));
container.RegisterSingle<ISiteMapBuilderSetStrategy>(() => new SiteMapBuilderSetStrategy(container.GetAllInstances<ISiteMapBuilderSet>().ToArray()));
}
private static IEnumerable<ISiteMapBuilderSet> ResolveISiteMapBuilderSets(Container container, bool securityTrimmingEnabled, bool enableLocalization)
{
yield return new SiteMapBuilderSet(
"default",
securityTrimmingEnabled,
enableLocalization,
container.GetInstance<ISiteMapBuilder>(),
container.GetInstance<ICacheDetails>());
}
private static void AllowToResolveArraysAndLists(Container container)
{
container.ResolveUnregisteredType += (sender, e) =>
{
var serviceType = e.UnregisteredServiceType;
if (serviceType.IsArray)
{
RegisterArrayResolver(e, container,
serviceType.GetElementType());
}
else if (serviceType.IsGenericType &&
serviceType.GetGenericTypeDefinition() == typeof(IList<>))
{
RegisterArrayResolver(e, container,
serviceType.GetGenericArguments()[0]);
}
};
}
private static void RegisterArrayResolver(UnregisteredTypeEventArgs e, Container container, Type elementType)
{
var producer = container.GetRegistration(typeof(IEnumerable<>)
.MakeGenericType(elementType));
var enumerableExpression = producer.BuildExpression();
var arrayMethod = typeof(Enumerable).GetMethod("ToArray")
.MakeGenericMethod(elementType);
var arrayExpression = Expression.Call(arrayMethod, enumerableExpression);
e.Register(arrayExpression);
}
}
but still i get the following exception:
No registration for type DynamicSiteMapNodeBuilder could be found and
an implicit registration could not be made. The constructor of the
type DynamicSiteMapNodeBuilder contains the parameter of type
ISiteMapNodeCreator with name 'siteMapNodeCreator' that is not
registered. Please ensure ISiteMapNodeCreator is registered in the
container, or change the constructor of DynamicSiteMapNodeBuilder.
First of all, to integrate with an existing DI setup, you should install MvcSiteMapProvider.MVC4.DI.SimpleInjector.Modules instead of MvcSiteMapProvider.MVC4.DI.SimpleInjector. You can downgrade by running this command from package manager console:
PM> Uninstall-Package -Id MvcSiteMapProvider.MVC4.DI.SimpleInjector
Be sure NOT to uninstall any dependencies. This will ensure that you don't have 2 sets of DI initialization code in your project - there should only be 1 for the entire application.
Next, you need to wire up for DI as well as some other initialization code required by MvcSiteMapProvider. The readme file contains instructions how to do this. Here is how you would do it with your existing configuration.
public static void Initialize()
{
Injection.Global = new Container();
InitializeContainer(Injection.Global);
Injection.Global.RegisterMvcControllers(Assembly.GetExecutingAssembly());
Injection.Global.RegisterMvcAttributeFilterProvider();
Injection.Global.Verify();
DependencyResolver.SetResolver(new SimpleInjectorDependencyResolver(Injection.Global));
}
private static void InitializeContainer(Container container)
{
// Setup configuration of DI (required)
MvcSiteMapProviderContainerInitializer.SetUp(container);
// Setup global sitemap loader (required)
MvcSiteMapProvider.SiteMaps.Loader = container.GetInstance<ISiteMapLoader>();
// Check all configured .sitemap files to ensure they follow the XSD for MvcSiteMapProvider (optional)
var validator = container.GetInstance<ISiteMapXmlValidator>();
validator.ValidateXml(HostingEnvironment.MapPath("~/Mvc.sitemap"));
// Register the Sitemaps routes for search engines (optional)
XmlSiteMapController.RegisterRoutes(RouteTable.Routes); // NOTE: You can put this in your RouteConfig.cs file if desired.
//... register some other stuff for your project here ...
}
If the /sitemap.xml endpoint doesn't work, you may also need to add this line to register the XmlSiteMapController:
Injection.Global.RegisterMvcControllers(typeof(MvcSiteMapProvider.SiteMaps).Assembly);
To implement ISiteMapNodeProvider, there is an example here: MvcSiteMapProvider ISiteMapBuilder in conjunction with IDynamicNodeProvider.
To register your custom ISiteMapNodeProvider, you just need to ensure it gets added to the constructor of SiteMapBuilder. You can also exclude the existing SiteMapNodeProviders from the code below depending on your needs.
// Register the sitemap node providers
container.RegisterSingle<XmlSiteMapNodeProvider>(() => container.GetInstance<XmlSiteMapNodeProviderFactory>()
.Create(container.GetInstance<IXmlSource>()));
container.RegisterSingle<ReflectionSiteMapNodeProvider>(() => container.GetInstance<ReflectionSiteMapNodeProviderFactory>()
.Create(includeAssembliesForScan));
// Register your custom sitemap node provider
container.RegisterSingle<ISiteMapNodeProvider, CustomSiteMapNodeProvider>();
// Register the collection of sitemap node providers (including the custom one)
container.RegisterSingle<ISiteMapBuilder>(() => container.GetInstance<SiteMapBuilderFactory>()
.Create(new CompositeSiteMapNodeProvider(
container.GetInstance<XmlSiteMapNodeProvider>(),
container.GetInstance<ReflectionSiteMapNodeProvider>(),
container.GetInstance<CustomSiteMapNodeProvider>())));
Do note that IDynamicNodeProvider (which is documented) does almost exactly the same thing as ISiteMapNodeProvider, so you could use that option instead. There are 3 main differences:
With IDynamicNodeProvider, you must create a "template" node that defines the dynamicNodeProvider attribute, and the template node itself won't be included in the SiteMap, so it must be used in conjunction with a ISiteMapNodeProvider implementation that processes the dynamic nodes (the built-in ISiteMapNodeProviders do this automatically).
IDynamicNodeProvider doesn't need to be part of the DI setup because it is already processed by both XmlSiteMapNodeProvider and ReflectionSiteMapNodeProvider.
With ISiteMapNodeProvider, you are working directly with the ISiteMapNode object, with IDynamicNodeProvider you are working with an abstraction (DynamicNodeProvider) and there is a conversion that happens automatically.
About SimpleInjector.Verify
If you want Verify() to work, you need to add the following to the excludeTypes array in the MvcSiteMapProviderContainerInitializer.
typeof(SiteMapNodeCreator),
typeof(DynamicSiteMapNodeBuilder)
I have added them to the module and will be in the next version of the Nuget package, but these modules do not update so you have to do it manually.
Note that the Verify() method tries to create an instance of everything that is registered with the container - including objects that never get created by the container in the real world. Therefore, if you use the Verify() method you have to be more diligent that something is not accidentally registered. This makes convention-based registration more difficult to do.
Ayende has an article about how to implement a simple audit trail for NHibernate (here) using event handlers.
Unfortunately, as can be seen in the comments, his implementation causes the following exception to be thrown: collection xxx was not processed by flush()
The problem appears to be the implicit call to ToString on the dirty properties, which can cause trouble if the dirty property is also a mapped entity.
I have tried my hardest to build a working implementation but with no luck.
Does anyone know of a working solution?
I was able to solve the same problem using following workaround: set the processed flag to true on all collections in the current persistence context within the listener
public void OnPostUpdate(PostUpdateEvent postEvent)
{
if (IsAuditable(postEvent.Entity))
{
//skip application specific code
foreach (var collection in postEvent.Session.PersistenceContext.CollectionEntries.Values)
{
var collectionEntry = collection as CollectionEntry;
collectionEntry.IsProcessed = true;
}
//var session = postEvent.Session.GetSession(EntityMode.Poco);
//session.Save(auditTrailEntry);
//session.Flush();
}
}
Hope this helps.
The fix should be the following. Create a new event listener class and derive it from NHibernate.Event.Default.DefaultFlushEventListener:
[Serializable]
public class FixedDefaultFlushEventListener: DefaultFlushEventListener
{
private static readonly log4net.ILog log = log4net.LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);
protected override void PerformExecutions(IEventSource session)
{
if (log.IsDebugEnabled)
{
log.Debug("executing flush");
}
try
{
session.ConnectionManager.FlushBeginning();
session.PersistenceContext.Flushing = true;
session.ActionQueue.PrepareActions();
session.ActionQueue.ExecuteActions();
}
catch (HibernateException exception)
{
if (log.IsErrorEnabled)
{
log.Error("Could not synchronize database state with session", exception);
}
throw;
}
finally
{
session.PersistenceContext.Flushing = false;
session.ConnectionManager.FlushEnding();
}
}
}
Register it during NHibernate configuraiton:
cfg.EventListeners.FlushEventListeners = new IFlushEventListener[] { new FixedDefaultFlushEventListener() };
You can read more about this bug in Hibernate JIRA:
https://hibernate.onjira.com/browse/HHH-2763
The next release of NHibernate should include that fix either.
This is not easy at all. I wrote something like this, but it is very specific to our needs and not trivial.
Some additional hints:
You can test if references are loaded using
NHibernateUtil.IsInitialized(entity)
or
NHibernateUtil.IsPropertyInitialized(entity, propertyName)
You can cast collections to the IPersistentCollection. I implemented an IInterceptor where I get the NHibernate Type of each property, I don't know where you can get this when using events:
if (nhtype.IsCollectionType)
{
var collection = previousValue as NHibernate.Collection.IPersistentCollection;
if (collection != null)
{
// just skip uninitialized collections
if (!collection.WasInitialized)
{
// skip
}
else
{
// read collections previous values
previousValue = collection.StoredSnapshot;
}
}
}
When you get the update event from NHibernate, the instance is initialized. You can safely access properties of primitive types. When you want to use ToString, make sure that your ToString implementation doesn't access any referenced entities nor any collections.
You may use NHibernate meta-data to find out if a type is mapped as an entity or not. This could be useful to navigate in your object model. When you reference another entity, you will get additional update events on this when it changed.
I was able to determine that this error is thrown when application code loads a Lazy Propery where the Entity has a collection.
My first attempt involed watching for new CollectionEntries (which I've never want to process as there shouldn't actually be any changes). Then mark them as IsProcessed = true so they wouldn't cause problems.
var collections = args.Session.PersistenceContext.CollectionEntries;
var collectionKeys = args.Session.PersistenceContext.CollectionEntries.Keys;
var roundCollectionKeys = collectionKeys.Cast<object>().ToList();
var collectionValuesClount = collectionKeys.Count;
// Application code that that loads a Lazy propery where the Entity has a collection
var postCollectionKeys = collectionKeys.Cast<object>().ToList();
var newLength = postCollectionKeys.Count;
if (newLength != collectionValuesClount) {
foreach (var newKey in postCollectionKeys.Except(roundCollectionKeys)) {
var collectionEntry = (CollectionEntry)collections[newKey];
collectionEntry.IsProcessed = true;
}
}
However this didn't entirly solve the issue. In some cases I'd still get the exception.
When OnPostUpdate is called the values in the CollectionEntries dictionary should all already be set to IsProcessed = true. So I decided to do an extra check to see if the collections not processed matched what I expected.
var valuesNotProcessed = collections.Values.Cast<CollectionEntry>().Where(x => !x.IsProcessed).ToList();
if (valuesNotProcessed.Any()) {
// Assert: valuesNotProcessed.Count() == (newLength - collectionValuesClount)
}
In the cases that my first attempt fixed these numbers would match exactly. However in the cases where it didn't work there were extra items alreay in the dictionary. In my I could be sure these extra items also wouldn't result in updates so I could just set IsProcessed = true for all the valuesNotProcessed.