I have a very basic WebAPI setup with token authentication.
In the application start I do:
protected void Application_Start()
{
DependencyConfig.RegisterDependecis();
//...
//...
}
Which calls:
public class DependencyConfig
{
private static ServiceContainer _LightInjectContainer;
public static ServiceContainer LightInjectContainer
{
get { return _LightInjectContainer; }
}
public static void RegisterDependecis()
{
var container = new LightInject.ServiceContainer();
container.RegisterApiControllers();
container.ScopeManagerProvider = new PerLogicalCallContextScopeManagerProvider();
container.EnableWebApi(GlobalConfiguration.Configuration);
container.Register<IRegistrationManager, RegistrationManager>(new PerScopeLifetime());
_LightInjectContainer = container;
}
}
Now, when the client invokes the token endpoint (requests a token), the provider I defined here:
OAuthOptions = new OAuthAuthorizationServerOptions
{
//...
//...
Provider = new SimpleAuthorizationServerProvider()
//...
//...
};
Is being used with this method:
public class SimpleAuthorizationServerProvider : OAuthAuthorizationServerProvider
{
//...
public override async Task GrantResourceOwnerCredentials(OAuthGrantResourceOwnerCredentialsContext context)
{
//...
// Here I get the exception!
var registrationManager = DependencyConfig.LightInjectContainer.GetInstance<IRegistrationManager>();
//...
}
//...
}
And when I try to get the instance the following error:
Attempt to create a scoped instance without a current scope.
I know the LightInject has a concept of Start/End scope for each request and It's actually telling me that no scope was started. But I can't seem to figure what exactly is broken and needs to be fixed.
By reading on of the last answers in this question, I came up with this solution: (Starting a scope manually)
using(DependencyConfig.LightInjectContainer.BeginScope())
{
IRegistrationManager manager = DependencyConfig.LightInjectContainer.GetInstance<IRegistrationManager>();
}
Technicaly it works, but I not sure if it's the right solution regarding whats happening behind the scenes.
I am the author of LightInject
Can you try this inside your handler(SimpleAuthorizationServerProvider)
request.GetDependencyScope().GetService(typeof(IRegistrationManager)) as IRegistrationManager;
There is actually no reason that you should expose the container as a static public member as this makes it very easy to start using the service locator anti-pattern.
Take a look at this blog post for more information.
http://www.strathweb.com/2012/11/asp-net-web-api-and-dependencies-in-request-scope/
Related
When setting up a MartenDB datastore in ASP.Net Core, you normally put code like this in your Startup.cs:
services.AddMarten(o =>
{
o.Connection(configuration.GetConnectionString("MyDatabase"));
o.AutoCreateSchemaObjects = AutoCreate.All;
o.Serializer(new JsonNetSerializer { EnumStorage = EnumStorage.AsString });
});
This allows you to then inject IDocumentSession and IDocumentStore into your various classes for working with that database.
Now what do you do if you have to connect to a second database? I looked at the ISessionFactory but it is not apparent that you can change the connection string from here. Do you need to manually create and register a new DocumentStore?
To answer my own question, I wound up creating a custom DocumentStore and ISessionFactory for each database I wanted to connect to, and then injecting the custom SessionFactory.
Here's the code (only showing one instance of each class for the sake of brevity. Just replace Db1 with Db2 for the second version of each class):
The custom DocumentStore:
public class Db1Store : DocumentStore
{
public Db1Store(StoreOptions options) : base(options)
{
}
}
The custom SessionFactory:
public class Db1SessionFactory : ISessionFactory
{
private readonly Db1Store store;
public Db1SessionFactory(Db1Store store)
{
this.store = store;
}
public IQuerySession QuerySession()
{
return store.QuerySession();
}
public IDocumentSession OpenSession()
{
return store.OpenSession();
}
}
The service registration (this replaces the services.AddMarten call):
services.AddSingleton(p =>
{
var options = new StoreOptions();
options.Connection(configuration.GetConnectionString("DB1"));
options.AutoCreateSchemaObjects = AutoCreate.All;
options.Serializer(new JsonNetSerializer { EnumStorage = EnumStorage.AsString });
return new Db1Store(options);
});
services.AddSingleton<Db1SessionFactory>();
Then you inject the Db1SessionFactory instance into your class, and run a query like this:
var result = await db1SessionFactory.QuerySession().Query<MyAwesomeTable>().ToListAsync();
Downsides:
I would prefer to inject the QuerySession or DocumentSession, but I can't see a way to do that without moving to Autofac or a similar DI Container that supports named instances.
I am not sure what downsides there will be creating these QuerySession/DocumentSessions in this manner. It may be a bad tradeoff.
I have spent over two weeks searching google, bing, stack overflow, and msdn docs trying to figure out how to do a proper dependency injection for a mobile app that I am developing. To be clear, I do DI every day in web apps. I do not need a crash course on what, who, and why DI is important. I know it is, and am always embracing it.
What I need to understand is how this works in a mobile app world, and in particular a UWP Template 10 Mobile app.
From my past, in a .net/Asp app I can "RegisterType(new XYZ).Singleton() blah" {please forgive syntax; just an example} in App_Start.ConfigureServices. This works almost identical in .netcore, granted some syntactic changes.
My problem is now I am trying to provide my api is going to an UWP app that needs to digest my IXYZ service. By no means do I think that they should "new" up an instance every time. There has to be a way to inject this into a container on the UWP side; and I feel I am missing something very simple in the process.
Here is the code I have:
App.xaml.cs
public override async Task OnStartAsync(StartKind startKind, IActivatedEventArgs args)
{
// TODO: add your long-running task here
//if (args.Kind == ActivationKind.LockScreen)
//{
//}
RegisterServices();
await NavigationService.NavigateAsync(typeof(Views.SearchCompanyPage));
}
public static IServiceProvider Container { get; private set; }
private static void RegisterServices()
{
var services = new ServiceCollection();
services.AddSingleton<IXYZ, XYZ>();
Container = services.BuildServiceProvider();
}
MainPage.xaml.cs:
public MainPage()
{
InitializeComponent();
NavigationCacheMode = NavigationCacheMode.Enabled;
}
MainPageViewModel:
public class MainPageViewModel : ViewModelBase
{
private readonly IXYZ _xyz;
public MainPageViewModel(IXYZ xyz)
{
//Stuff
_xyz= xyz;
}
}
I now get the error:
XAML MainPage...ViewModel type cannot be constructed. In order to be constructed in XAML, a type cannot be abstract, interface nested generic or a struct, and must have a public default constructor.
I am willing to use any brand of IoC Container, but what I need is an example of how to properly use DI for services in a UWP app. 99.9% of questions about DI is about Views (i.e. Prism?) not just a simple DI for a service (i.e. DataRepo; aka API/DataService).
Again, I feel I am missing something obvious and need a nudge in the right direction. Can somebody show me an example project, basic code, or a base flogging on how I should not be a programmer...please don't do that (I don't know if my ego could take it).
You can try to Microsoft.Hosting.Extensions just like ASP.NET, there's an implementation on Xamarin.Forms by James Montemagno, as well it can be used in UWP I have tried and it works perfectly. You have to change some parts in order to get it working.
In OnLaunched Method add Startup.Init();
public static class Startup
{
public static IServiceProvider ServiceProvider { get; set; }
public static void Init()
{
StorageFolder LocalFolder = ApplicationData.Current.LocalFolder;
var configFile = ExtractResource("Sales.Client.appsettings.json", LocalFolder.Path);
var host = new HostBuilder()
.ConfigureHostConfiguration(c =>
{
// Tell the host configuration where to file the file (this is required for Xamarin apps)
c.AddCommandLine(new string[] { $"ContentRoot={LocalFolder.Path}" });
//read in the configuration file!
c.AddJsonFile(configFile);
})
.ConfigureServices((c, x) =>
{
// Configure our local services and access the host configuration
ConfigureServices(c, x);
}).
ConfigureLogging(l => l.AddConsole(o =>
{
//setup a console logger and disable colors since they don't have any colors in VS
o.DisableColors = true;
}))
.Build();
//Save our service provider so we can use it later.
ServiceProvider = host.Services;
}
static void ConfigureServices(HostBuilderContext ctx, IServiceCollection services)
{
//ViewModels
services.AddTransient<HomeViewModel>();
services.AddTransient<MainPageViewModel>();
}
static string ExtractResource(string filename, string location)
{
var a = Assembly.GetExecutingAssembly();
using (var resFilestream = a.GetManifestResourceStream(filename))
{
if (resFilestream != null)
{
var full = Path.Combine(location, filename);
using (var stream = File.Create(full))
{
resFilestream.CopyTo(stream);
}
}
}
return Path.Combine(location, filename);
}
}
Injecting a ViewModel is possible as well which is pretty nice.
With help from #mvermef and the SO question Dependency Injection using Template 10 I found a solutions. This turned out to be a rabbit hole where at every turn I ran into an issue.
The first problem was just getting Dependency Injection to work. Once I was able to get that figured out from the sources above I was able to start injecting my services into ViewModels and setting them to the DataContext in the code behind.
Then I ran into an injection issue problem with injecting my IXYZ services into the ViewModels of UserControls.
Pages and their ViewModels worked great but I had issues with the DataContext of the UserControl not being injected with UserControl's ViewModel. They were instead getting injected by the Page's ViewModel that held it.
The final solution turned out to be making sure that the UserControl had the DataContext being set in XAML not the code behind, as we did with the Pages, and then creating a DependencyProperty in the code behind.
To show the basic solution read below.
To make it work I started with:
APP.XAML.CS
public override async Task OnStartAsync(StartKind startKind, IActivatedEventArgs args)
{
// long-running startup tasks go here
RegisterServices();
await Task.CompletedTask;
}
private static void RegisterServices()
{
var services = new ServiceCollection();
services.AddSingleton<IRepository, Repository>();
services.AddSingleton<IBinderService, BinderServices>();
**//ViewModels**
**////User Controls**
services.AddSingleton<AddressesControlViewModel, AddressesControlViewModel>();
services.AddSingleton<CompanyControlViewModel, CompanyControlViewModel>();
**//ViewModels**
**////Pages**
services.AddSingleton<CallListPageViewModel, CallListPageViewModel>();
services.AddSingleton<CallListResultPageViewModel, CallListResultPageViewModel>();
etc....
Container = services.BuildServiceProvider();
}
public override INavigable ResolveForPage(Page page, NavigationService navigationService)
{
**//INJECT THE VIEWMODEL FOR EACH PAGE**
**//ONLY THE PAGE NOT USERCONTROL**
if (page is CallListPage)
{
return Container.GetService<CallListPageViewModel>();
}
if (page is CallListResultPage)
{
return Container.GetService<CallListResultPageViewModel>();
}
etc...
return base.ResolveForPage(page, navigationService);
}
In the code behind for the Page
CALLLISTPAGE.XAML.CS
public CallListPage()
{
InitializeComponent();
}
CallListPageViewModel _viewModel;
public CallListPageViewModel ViewModel
{
get { return _viewModel ?? (_viewModel = (CallListPageViewModel)DataContext); }
}
In your XAML add your UserControl
CALLLISTPAGE.XAML
<binder:CompanyControl Company="{x:Bind ViewModel.SelectedCompany, Mode=TwoWay}"/>
In your UserControl make sure to add the DataContext to the XAML NOT the code behind like we did with the pages.
COMPANYCONTROL.XAML
<UserControl.DataContext>
<viewModels:CompanyControlViewModel x:Name="ViewModel" />
</UserControl.DataContext>
In the UserControl Code Behind add a Dependency Property
COMPANYCONTROL.XAML.CS
public static readonly DependencyProperty CompanyProperty = DependencyProperty.Register(
"Company", typeof(Company), typeof(CompanyControl), new PropertyMetadata(default(Company), SetCompany));
public CompanyControl()
{
InitializeComponent();
}
public Company Company
{
get => (Company) GetValue(CompanyProperty);
set => SetValue(CompanyProperty, value);
}
private static void SetCompany(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var control = d as CompanyControl;
var viewModel = control?.ViewModel;
if (viewModel != null)
viewModel.Company = (Company) e.NewValue;
}
In the end I am not sure if this is an elegant solution but it works.
I'm wanting to configure registrations in a Unity container being used by ASP.NET Web API 2 based on properties of a HTTP request. For example, a request to /api/database1/values should result in a Unity container configuration with an IDbContext configured for database1, while a request to /api/database4/values will get an IDbContext configured for database4.
I've gotten so far as using UnityHierarchicalDependencyResolver as the dependency resolver, so types registered with HierarchicalLifetimeManager last only for the lifetime of the request. This works well for getting types resolved per request. But how to get them registered per request using OWIN middleware is beyond me.
In my middleware, a call to System.Web.Http.GlobalConfiguration.Configuration.DependencyResolver.GetService(typeof(IUnityContainer)) gets an instance of IUnityContainer, but it's the same container for all requests, including any registrations from previous requests.
By encapsulating UnityHierarchicalDependencyResolver with my own implementation of IDependencyResolver I can see that IDependencyResolver.BeginScope isn't called until much later in the process. So the problem would seem to be that the child container isn't created until Web API wakes up, long after my middleware calls Next(..).
Is there a way I can get the scope of my dependency resolver to start sooner? Is there some other strategy that I'm missing. In case it makes any difference, I'm hosting in IIS, but favouring the OWIN middleware approach.
Update
This isn't an answer, and it's too big for a comment, but after struggling to solve this with Unity I decided to switch to Autofac and it all just fell into place.
The Autofac OWIN packages (Autofac.Mvc5.Owin, Autofac.Owin, Autofac.WebApi2.Owin) make it dead easy to use Autofac within the OWIN pipeline and ensure appropriate lifetime management in ASP.NET MVC and Web API. This was the missing link.
I couldn't find a way to reconfigure the container per-request, but it did at least make it possible to configure a factory per-request (so yes, #Haukinger and #alltej, you were right to push in that direction.
So I register a factory like:
builder.RegisterType<DataDependencyFactory>().InstancePerRequest();
And register the create method of that factory like:
builder
.Register(c => c.Resolve<DataDependencyFactory>().CreateDataDependency())
.As<IDataDependency>()
.InstancePerRequest();
Registering the factory this way is particularly useful, because downstream dependents don't need to be aware of the factory. I like this because my dependents don't need a factory, they need an instance. The container bends to the needs of my dependents, not the other way around :)
Then, in a piece of OWIN middleware, I resolve the factory, and set a property on it according to the properties of the request. Subsequent resolution of IDataDependency in an MVC or Web API controller, or anything else later in the OWIN pipeline, will get an instance configured according to the property on the factory.
Based on your api URL ("/api/database4/values"), I suggest that you create a filter attribute(e.g. DbIdFilter) so that you can reuse the filter attribute to other controller methods that follow similar url path/segment like this below:
[HttpGet]
[DbIdFilter]
[Route("{databaseId}/values")]
public IHttpActionResult GetValues()
{
return Ok();
}
[HttpGet]
[DbIdFilter]
[Route("{databaseId}/products")]
public IHttpActionResult GetProducts()
{
return Ok();
}
First, create the filter attribute:
public class DbIdFilterAttribute : ActionFilterAttribute
{
private readonly string _routeDataId;
private const string defaultRouteName = "databaseId";
public DbIdFilterAttribute():this(defaultRouteName)
{}
public DbIdFilterAttribute(string routeDataId)
{
_routeDataId = routeDataId;
}
public override void OnActionExecuting(HttpActionContext actionContext)
{
var routeData = actionContext.Request.GetRouteData();
var dbId = routeData.Values[_routeDataId] as string;
//here we create the db instance at the filter level.
DbInstanceFactory.RegisterDbInstance(dbId);
}
}
Next, create an instance factory that will register/resolve the db instance during runtime:
public class DbInstanceFactory : IDbInstanceFactory
{
public static IDbInstance RegisterDbInstance(string databaseId)
{
var factory = UnityConfig.GetConfiguredContainer().Resolve<IDbInstanceFactory>();
return factory.CreateInstance(databaseId);
}
public IDbInstance CreateInstance(string databaseId)
{
var container = UnityConfig.GetConfiguredContainer();
//container.RegisterType<IDbInstance, DbInstance>();
container.RegisterType<IDbInstance, DbInstance>(new InjectionConstructor(databaseId));
var dbInstance = container.Resolve<IDbInstance>();
return dbInstance;
}
public IDbInstance GetInstance()
{
var container = UnityConfig.GetConfiguredContainer();
var dbInstance = container.Resolve<IDbInstance>();
return dbInstance;
}
}
public interface IDbInstanceFactory
{
IDbInstance CreateInstance(string databaseId);
IDbInstance GetInstance();
}
Register this factory class in UnityConfig.cs (or wherever you currently register the types):
container.RegisterType<IDbInstanceFactory, DbInstanceFactory>
(new ContainerControlledLifetimeManager());
It's registered ContainerControlledLifetimeManager since this factory does not have to be a per request.
So just a basic DbInstance class below(for clarity) that takes a parameter in the constructor (this parameter can be your connection string or a named connection):
public class DbInstance : IDbInstance
{
public string DbId { get; }
public DbInstance(string databaseId)
{
DbId = databaseId;
}
}
public interface IDbInstance
{
string DbId { get; }
}
In controller class, you can use it like this:
....
private IDbInstanceFactory _dbFactory;
public MyController(IDbInstanceFactory dbFactory)
{
_dbFactory = dbFactory;
}
// Alternate, if you want to use property injection instead of constructor injection
//[Dependency]
//public IDbInstanceFactory DbFactory { get; set; }
[HttpGet]
[DbIdFilter]
[Route("{databaseId}/test")]
public IHttpActionResult Test()
{
var db = _dbFactory.GetInstance();
return Ok(db.DbId);
}
...
I've read and Googled everything on this, but can't seem to get it to work. I created a custom LifetimeManager for Unity in my MVC5 application based on these posts:
MVC3 Unity Framework and Per Session Lifetime Manager
This may be the issue I am experiencing
Here is my SessionLifetimeManager
public class SessionLifetimeManager : LifetimeManager
{
private string key = Guid.NewGuid().ToString();
public override object GetValue()
{
return HttpContext.Current.Session[key];
}
public override void RemoveValue()
{
HttpContext.Current.Session.Remove(key);
}
public override void SetValue(object newValue)
{
HttpContext.Current.Session[key] = newValue;
}
}
I only have a few types I'm playing with, here is the relevant registrations in UnityConfig.cs:
container.RegisterType<IEpiSession, EpiSession>(new SessionLifetimeManager(),
new InjectionConstructor(config.AppServerURI, config.PathToSysConfig));
container.RegisterType<IReportRepository, EpicorReportRepository>(new TransientLifetimeManager());
DependencyResolver.SetResolver(new UnityDependencyResolver(container));
Note that the EpicorReportRepository has a dependency on IEpiSession via constructor injection.
public class EpicorReportRepository : IReportRepository
{
private IEpiSession session;
// DI constructor
public EpicorReportRepository(IEpiSession session) {
this.session = session;
}
// ...
}
My Problem: After the first user / session connects to the application, every new user / session after that seems to still be using the EpiSession object and credentials that the first user had create/injected for him. This seems to be a common pattern used on the interwebs, so I'm wondering what I am missing.
How did you test that IEpiSession is the same in different Sessions?
Try to open you application from different browsers. If you open several tabs in the same browser then the same session is used.
I checked your code and it works for me.
There is the only one difference in SetResolver():
DependencyResolver.SetResolver(
type => container.Resolve(type),
types => container.ResolveAll(types));
The full registration code is the following:
public class MvcApplication : System.Web.HttpApplication
{
protected void Application_Start()
{
...
var container = new UnityContainer();
container.RegisterType<IEpiSession, EpiSession>(
new SessionLifetimeManager(),
new InjectionConstructor("config.AppServerURI", "config.PathToSysConfig"));
container.RegisterType<IReportRepository, EpicorReportRepository>(new TransientLifetimeManager());
DependencyResolver.SetResolver(
type => container.Resolve(type),
types => container.ResolveAll(types));
}
}
I have implemented a service which uses a DAOFactory and a NHibernate Helper for the sessions and transactions. The following code is very much simplified:
public interface IService
{
IList<Disease> getDiseases();
}
public class Service : IService
{
private INHibernateHelper NHibernateHelper;
private IDAOFactory DAOFactory;
public Service(INHibernateHelper NHibernateHelper, IDAOFactory DAOFactory)
{
this.NHibernateHelper = NHibernateHelper;
this.DAOFactory = DAOFactory;
}
public IList<Disease> getDiseases()
{
return DAOFactory.getDiseaseDAO().FindAll();
}
}
public class NHibernateHelper : INHibernateHelper
{
private static ISessionFactory sessionFactory;
/// <summary>
/// SessionFactory is static because it is expensive to create and is therefore at application scope.
/// The property exists to provide 'instantiate on first use' behaviour.
/// </summary>
private static ISessionFactory SessionFactory
{
get
{
if (sessionFactory == null)
{
try
{
sessionFactory = new Configuration().Configure().AddAssembly("Bla").BuildSessionFactory();
}
catch (Exception e)
{
throw new Exception("NHibernate initialization failed.", e);
}
}
return sessionFactory;
}
}
public static ISession GetCurrentSession()
{
if (!CurrentSessionContext.HasBind(SessionFactory))
{
CurrentSessionContext.Bind(SessionFactory.OpenSession());
}
return SessionFactory.GetCurrentSession();
}
public static void DisposeSession()
{
var session = GetCurrentSession();
session.Close();
session.Dispose();
}
public static void BeginTransaction()
{
GetCurrentSession().BeginTransaction();
}
public static void CommitTransaction()
{
var session = GetCurrentSession();
if (session.Transaction.IsActive)
session.Transaction.Commit();
}
public static void RollbackTransaction()
{
var session = GetCurrentSession();
if (session.Transaction.IsActive)
session.Transaction.Rollback();
}
}
At the end of the day I just want to expose the IService to ASP.NET MVC/Console application/Winform. I can already use the Service in a console application but would like to improve it first. I guess the first improvement would be to inject the interfaces INHibernateHelper and IDAOFactory via castle. But I think the problem is that the NHibernateHelper might cause problems in a asp.net context where NHibernateHelper should run according to the 'Nhibernate session per request' pattern. One question I have is whether this pattern is determined by the nhibernate config section (setting current_session_context_class = web) or can i control this via castle somehow?
I hope this makes sense. The final aim is just to expose THE IService.
Thanks.
Christian
You have two choices..
1) Host it in WCF. This allows you access from any source you want.
2) Abstract away everything that's specific to how the code is being used. In our system for instance we use our own Unit Of Work implementation which is stored differently based on where the code is running. A small example would be storing something using the WCF call context vs. the current thread.