I have been doing my first Test Driven Development project recently and have been learning Ninject and MOQ. This is my first attempt at all this. I've found the TDD approach has been thought provoking, and Ninject and MOQ have been great. The project I am working on has not particularly been the best fit for Ninject as it is a highly configurable C# program that is designed to test the use of a web service interface.
I have broken it up into modules and have interfaces all over the shop, but I am still finding that I am having to use lots of constructor arguments when getting an implementation of a service from the Ninject kernel. For example;
In my Ninject module;
Bind<IDirEnum>().To<DirEnum>()
My DirEnum class;
public class DirEnum : IDirEnum
{
public DirEnum(string filePath, string fileFilter,
bool includeSubDirs)
{
....
In my Configurator class (this is the main entry point) that hooks all the services together;
class Configurator
{
public ConfigureServices(string[] args)
{
ArgParser argParser = new ArgParser(args);
IDirEnum dirEnum = kernel.Get<IDirEnum>(
new ConstructorArgument("filePath", argParser.filePath),
new ConstructorArgument("fileFilter", argParser.fileFilter),
new ConstructorArgument("includeSubDirs", argParser.subDirs)
);
filePath, fileFilter and includeSubDirs are command line options to the program. So far so good. However, being a conscientious kind of guy, I have a test covering this bit of code. I'd like to use a MOQ object. I have created a Ninject module for my tests;
public class TestNinjectModule : NinjectModule
{
internal IDirEnum mockDirEnum {set;get};
Bind<IDirEnum>().ToConstant(mockDirEnum);
}
And in my test I use it like this;
[TestMethod]
public void Test()
{
// Arrange
TestNinjectModule testmodule = new TestNinjectModule();
Mock<IDirEnum> mockDirEnum = new Mock<IDirEnum>();
testModule.mockDirEnum = mockDirEnum;
// Act
Configurator configurator = new Configurator();
configurator.ConfigureServices();
// Assert
here lies my problem! How do I test what values were passed to the
constructor arguments???
So the above shows my problem. How can I test what arguments were passed to the ConstructorArguments of the mock object? My guess is that Ninject is dispensing of the ConstuctorArguments in this case as the Bind does not require them? Can I test this with a MOQ object or do I need to hand code a mock object that implements DirEnum and accepts and 'records' the constructor arguments?
n.b. this code is 'example' code, i.e. I have not reproduced my code verbatim, but I think I have expressed enough to hopefully convey the issues? If you need more context, please ask!
Thanks for looking. Be gentle, this is my first time ;-)
Jim
There are a few problems with the way you designed your application. First of all, you are calling the Ninject kernel directly from within your code. This is called the Service Locator pattern and it is considered an anti-pattern. It makes testing your application much harder and you are already experiencing this. You are trying to mock the Ninject container in your unit test, which complicates things tremendously.
Next, you are injecting primitive types (string, bool) in the constructor of your DirEnum type. I like how MNrydengren states it in the comments:
take "compile-time" dependencies
through constructor parameters and
"run-time" dependencies through method
parameters
It's hard for me to guess what that class should do, but since you are injecting these variables that change at run-time into the DirEnum constructor, you end up with a hard to test application.
There are multiple ways to fix this. Two that come in mind are the use of method injection and the use of a factory. Which one is feasible is up to you.
Using method injection, your Configurator class will look like this:
class Configurator
{
private readonly IDirEnum dirEnum;
// Injecting IDirEnum through the constructor
public Configurator(IDirEnum dirEnum)
{
this.dirEnum = dirEnum;
}
public ConfigureServices(string[] args)
{
var parser = new ArgParser(args);
// Inject the arguments into a method
this.dirEnum.SomeOperation(
argParser.filePath
argParser.fileFilter
argParser.subDirs);
}
}
Using a factory, you would need to define a factory that knows how to create new IDirEnum types:
interface IDirEnumFactory
{
IDirEnum CreateDirEnum(string filePath, string fileFilter,
bool includeSubDirs);
}
Your Configuration class can now depend on the IDirEnumFactory interface:
class Configurator
{
private readonly IDirEnumFactory dirFactory;
// Injecting the factory through the constructor
public Configurator(IDirEnumFactory dirFactory)
{
this.dirFactory = dirFactory;
}
public ConfigureServices(string[] args)
{
var parser = new ArgParser(args);
// Creating a new IDirEnum using the factory
var dirEnum = this.dirFactory.CreateDirEnum(
parser.filePath
parser.fileFilter
parser.subDirs);
}
}
See how in both examples the dependencies get injected into the Configurator class. This is called the Dependency Injection pattern, opposed to the Service Locator pattern, where the Configurator asks for its dependencies by calling into the Ninject kernel.
Now, since your Configurator is completely free from any IoC container what so ever, you can now easily test this class, by injecting a mocked version of the dependency it expects.
What is left is to configure the Ninject container in the top of your application (in DI terminology: the composition root). With the method injection example, your container configuration would stay the same, with the factory example, you will need to replace the Bind<IDirEnum>().To<DirEnum>() line with something as follows:
public static void Bootstrap()
{
kernel.Bind<IDirEnumFactory>().To<DirEnumFactory>();
}
Of course, you will need to create the DirEnumFactory:
class DirEnumFactory : IDirEnumFactory
{
IDirEnum CreateDirEnum(string filePath, string fileFilter,
bool includeSubDirs)
{
return new DirEnum(filePath, fileFilter, includeSubDirs);
}
}
WARNING: Do note that factory abstractions are in most cases not the best design, as explained here.
The last thing you need to do is to create a new Configurator instance. You can simply do this as follows:
public static Configurator CreateConfigurator()
{
return kernel.Get<Configurator>();
}
public static void Main(string[] args)
{
Bootstrap():
var configurator = CreateConfigurator();
configurator.ConfigureServices(args);
}
Here we call the kernel. Although calling the container directly should be prevented, there will always at least be one place in your application where you call the container, simply because it must wire everything up. However, we try to minimize the number of times the container is called directly, because it improves -among other things- the testability of our code.
See how I didn't really answer your question, but showed a way to work around the problem very effectively.
You might still want to test your DI configuration. That's very valid IMO. I do this in my applications. But for this, you often don't need the DI container, or even if your do, this doesn't mean that all your tests should have a dependency on the container. This relationship should only exist for the tests that test the DI configuration itself. Here is a test:
[TestMethod]
public void DependencyConfiguration_IsConfiguredCorrectly()
{
// Arrange
Program.Bootstrap();
// Act
var configurator = Program.CreateConfigurator();
// Assert
Assert.IsNotNull(configurator);
}
This test indirectly depends on Ninject and it will fail when Ninject is not able to construct a new Configurator instance. When you keep your constructors clean from any logic and only use it for storing the taken dependencies in private fields, you can run this, without the risk of calling out to a database, web service or what so ever.
I hope this helps.
Related
I am trying to find out how I can pass the StructrueMap container to a class that I wrote that inherits from another (MS-Class).
namespace TheNamespace
{
public class DatabaseIssuerNameRegistry : ValidatingIssuerNameRegistry
{
/* **This can't be done**
public DatabaseIssuerNameRegistry(IPortalTenantManager portalTenantManager)
{
_someField= portalTenantManager;
}*/
protected override bool IsThumbprintValid(string thumbprint, string issuer)
{
//How does it work ???????????
var portalTenantManager = container.GetInstance<IPortalTenantManager>();
//Do something with the portalTenantManager
}
}
I need portalTenantManager to be the Instance that I have defined in my container in the Global.asax.
My Global Assax has these things setup:
protected void Application_Start()
{
var container = new Container();
container.Configure(x =>
{ ....
....
x.For<IPortalTenantManager>().Use<PortalTenantManager>();
});
...
...
ControllerBuilder.Current.SetControllerFactory(new StructureMapControllerFactory(container));
...
GlobalConfiguration.Configuration.DependencyResolver = new StructureMapApiControllerFactory(container);
...
}
Edit:
Because of the comments of #NightOwl888 I'll explain a bit further what this class does. (Hopefully explaining so why my hands are tied)
My application is able to authenticate a user with Azure Active Directory and is Multi-tenant capable. In the authentication pipeline I have the possibility to store the validation endpoints in my database instead of the default way on the web.config file. See MSDN
and this, which actually is explaining exactly what I'm doing.
So I registered my class in the web.config under the Tag issuerNameRegistry. At some point of the validation pipeline my class is instantiated and the overriden method IsThumbprintValid is beeing called. The problem is that the class registered in issuerNameRegistry expects a parameterless constructor (there it is! the constrained construction!), therefore I cannot create a constructor that would solve my problem.
Thanks for your help
It turns out that this question has been asked before on MSDN, the answer of which was provided by Travis Spencer in 2 different posts.
it is typical in my experience to have a single container and use that service- or Web-side-wide. In the startup of the service or Web app, you can create the container, register the dependencies, new up an instance of your SecurityTokenServiceConfiguration class, resolve your dependencies, use it to punch out a SecurityTokenService object, and host it.
After the first beta, we really pushed for DI support. We got a little hook in beta 2. You can now create a custom SecurityTokenServiceConfiguration class that overrides the virtual CreateSecurityTokenService method. The implementation in Microsoft's SecurityTokenServiceConfiguration does Activator.CreateInstance; yours can do IoC. This can include the resolution of an IssuerNameRegistiry. Something like this perhaps:
RequestSecurityTokenResponse Issue(IClaimsPrincipal principal, RequestSecurityToken request)
{
SecurityTokenServiceConfiguration config = new MyGoodSecurityTokenServiceConfiguration();
SecurityTokenService sts = config.CreateSecurityTokenService();
RequestSecurityTokenResponse rstr = sts.Issue(principal, request);
return rstr;
}
public class MyGoodSecurityTokenServiceConfiguration : SecurityTokenServiceConfiguration
{
public override SecurityTokenService CreateSecurityTokenService()
{
IssuerNameRegistry = IoC.Resolve<IssuerNameRegistry>();
var sts = IoC.Reslove<SecurityTokenService>();
return sts;
}
}
Of course, this means that you need to create a static instance of your DI container so it is accessible to your SecurityTokenServiceConfiguration class. Personally, I don't like that idea because it makes your DI container accessible throughout the application, which can lead to abuse of the DI container as a service locator.
Ideally, there would be a way in any DI friendly framework to pass the container into an abstract factory in order to resolve service dependencies. However, since I am not familiar with WIF it is unclear whether that can be done - perhaps the class where the Issue method exists could have a constructor added? The trick is to keep walking up the chain until you find the first place in the framework where you can intervene and do all of your DI configuration there.
We're trying to use MEF 2 with ASP.NET MVC 4 to support an extensible application. There are really 2 parts to this question (hope that's okay SO gods):
How do we use Microsoft.Composition and the MVC container code (MEF/MVC demo source) to replace Ninject as our DI for ICoreService, ICoreRepository, IUnitOfWork, and IDbContext?
It looks like we can't use both Ninject and the MVC container at the same time (I'm sure many are saying "duh"), so we'd like to go with MEF, if possible. I tried removing Ninject and setting [Export] attributes on each of the relevant implementations, spanning two assemblies in addition to the web project, but Save() failed to persist with no errors. I interpreted that as a singleton issue, but could not figure out how to sort it out (incl. [Shared]).
How do we load multiple assemblies dynamically at runtime?
I understand how to use CompositionContainer.AddAssemblies() to load specific DLLs, but for our application to be properly extensible, we require something more akin to how I (vaguely) understand catalogs in "full" MEF, which have been stripped out from the Microsoft.Composition package (I think?); to allow us to load all IPluggable (or whatever) assemblies, which will include their own UI, service, and repository layers and tie in to the Core service/repo too.
EDIT 1
A little more reading solved the first problem which was, indeed, a singleton issue. Attaching [Shared(Boundaries.HttpRequest)] to the CoreDbContext solved the persistence problem. When I tried simply [Shared], it expanded the 'singletonization' to the Application level (cross-request) and threw an exception saying that the edited object was already in the EF cache.
EDIT 2
I used the iterative assembly loading "meat" from Nick Blumhardt's answer below to update my Global.asax.cs code. The standard MEF 2 container from his code did not work in mine, probably because I'm using the MEF 2(?) MVC container. Summary: the code listed below now works as desired.
CoreDbContext.cs (Data.csproj)
[Export(typeof(IDbContext))]
[Shared(Boundaries.HttpRequest)]
public class CoreDbContext : IDbContext { ... }
CoreRepository.cs (Data.csproj)
[Export(typeof(IUnitOfWork))]
[Export(typeof(ICoreRepository))]
public class CoreRepository : ICoreRepository, IUnitOfWork
{
[ImportingConstructor]
public CoreRepository(IInsightDbContext context)
{
_context = context;
}
...
}
CoreService.cs (Services.csproj)
[Export(typeof(ICoreService))]
public class CoreService : ICoreService
{
[ImportingConstructor]
public CoreService(ICoreRepository repository, IUnitOfWork unitOfWork)
{
_repository = repository;
_unitOfWork = unitOfWork;
}
...
}
UserController.cs (Web.csproj)
public class UsersController : Controller
{
[ImportingConstructor]
public UsersController(ICoreService service)
{
_service = service;
}
...
}
Global.asax.cs (Web.csproj)
public class MvcApplication : System.Web.HttpApplication
{
protected void Application_Start()
{
CompositionProvider.AddAssemblies(
typeof(ICoreRepository).Assembly,
typeof(ICoreService).Assembly,
);
// EDIT 2 --
// updated code to answer my 2nd question based on Nick Blumhardt's answer
foreach (var file in System.IO.Directory.GetFiles(Server.MapPath("Plugins"), "*.dll"))
{
try
{
var name = System.Reflection.AssemblyName.GetAssemblyName(file);
var assembly = System.Reflection.Assembly.Load(name);
CompositionProvider.AddAssembly(assembly);
}
catch
{
// You'll need to craft exception handling to
// your specific scenario.
}
}
}
}
If I understand you correctly, you're looking for code that will load all assemblies from a directory and load them into the container; here's a skeleton for doing that:
var config = new ContainerConfiguration();
foreach (var file in Directory.GetFiles(#".\Plugins", "*.dll"))
{
try
{
var name = AssemblyName.GetAssemblyName(file);
var assembly = Assembly.Load(name);
config.WithAssembly(assembly);
}
catch
{
// You'll need to craft exception handling to
// your specific scenario.
}
}
var container = config.CreateContainer();
// ...
Hammett discusses this scenario and shows a more complete version in F# here: http://hammett.castleproject.org/index.php/2011/12/a-decent-directorycatalog-implementation/
Note, this won't detect assemblies added to the directory after the application launches - Microsoft.Composition isn't intended for that kind of use, so if the set of plug-ins changes your best bet is to detect that with a directory watcher and prompt the user to restart the app. HTH!
MEF is not intended to be used as DI framework. Which means that you should separate your "plugins" (whatever they are) composition from your infrastructure dependencies, and implement the former via MEF and the latter via whatever DI framework you prefer.
I think there are a little misunderstandings on what MEF can and can't do.
Originally MEF was conceived as purely an extensibility architecture, but as the framework evolved up to its first release, it can be fully supported as a DI container also. MEF will handle dependency injection for you, and does so through it's ExportProvider architecture. It is also entirely possible to use other DI frameworks with MEF. So in reality there are a number of ways things could be achieved:
Build a NinjectExportProvider that you can plug into MEF, so when MEF is searching for available exports, it will be able to interrogate your Ninject container.
Use an implementation of the Common Services Locator pattern to bridge between MEF and Ninject or vice versa.
Because you are using MEF for the extensibility, you'll probably want to use the former, as this exposes your Ninject components to MEF, which in turn exposes them to your plugins.
The other thing to consider, which is a bit disappointing, is in reality there isn't a lot of room for automagically plugging in of features ala Wordpress on ASP.NET. ASP.NET is a compiled and managed environment, and because of that you either resort to late-binding by loading assemblies manually at runtime, or you restart the application to pick up the new plugins, which sort of defeats the object of being able to plug new extensions in through the application.
My advice, is plan your architecture to pick up any extensibility points as startup and assume that any core changes will require a deployment and application restart.
In terms of the direct questions asked:
The CompositionProvider accepts in instance of ContainerConfiguration which is used internally to create the CompositionContainer used by the provider. So you could use this as the point by which you customise how you want your container to be instantiated. The ContainerConfiguration supports a WithProvider method:
var configuration = new ContainerConfiguration().WithProvider(new NinjectExportDescriptorProvider(kernel));
CompositionProvider.SetConfiguration(configuration);
Where NinjectExportDescriptorProvider might be:
public class NinjectExportDescriptorProvider: ExportDescriptorProvider
{
private readonly IKernel _kernel;
public NinjectExportDescriptorProvider(IKernel kernel)
{
if (kernel == null) throw new ArgumentNullException("kernel");
_kernel = kernel;
}
public override IEnumerable<ExportDescriptorPromise> GetExportDescriptors(
CompositionContract contract, DependencyAccessor dependencyAccessor)
{
var type = contract.ContractType;
if (!_kernel.GetBindings(type).Any())
return NoExportDescriptors;
return new[] {
new ExportDescriptorPromise(
contract,
"Ninject Kernel",
true, // Hmmm... need to consider this, setting it to true will create it as a shared part, false as new instance each time,
NoDependencies,
_ => ExportDescriptor.Create((c, o) => _kernel.Get(type), NoMetadata)) };
}
}
}
Note: I have not tested this, this is all theory, and is based on the example AppSettingsExportDescriptorProvider at: http://mef.codeplex.com/wikipage?title=ProgrammingModelExtensions
It's different from using the standard ExportProvider, because using the CompostionProvider is built around lightweight composition. But essentially you're wrapping up access to your Ninject kernel and making it available to your CompositionContainer.
As with adding a specific new provider (see above), you can use the ContainerConfiguration to read the available assemblies, probably something like:
var configuration = new ContainerConfiguration().WithAssemblies(AppDomain.GetAssemblies())
Again, I haven't tested all of this, but I hope it at least points you in the right direction.
Let's say we have class:
public class WithDependencies
{
public WithDependencies(IAmDependencyOne first, IAmDependencyTwo second)
// ...
}
Now the question. How do you create objects of WithDependencies class in an application?
I know there are many ways.
new WithDependencies(new DependencyOne(), new DependencyTwo());
new WithDependencies(IoC.Resolve(IDependencyOne), IoC.Resolve(IDependencyTwo());
// register IDependencyOne, IDependencyTwo implementations at app start
IoC.Resolve(WithDependencies);
// register IDependencyOne, IDependencyTwo implementations at app start
// isolate ourselves from concrete IoC Container
MyCustomWithDependenciesFactory.Create();
and so on...
What do you think is the way to do it?
Edit:
Because I don't get answers or I don't understand them I'll try to ask again. Let's say that on some event (button, timer, whatever) I need new object WithDependencies(). How do I create it? Assume IoC container is already configured.
It depends on the context, so it's impossible to provide a single answer. Conceptually you'd be doing something like this from the Composition Root:
var wd = new WithDependencies(new DependencyOne(), new DependencyTwo());
However, even in the absence of a DI Container, the above code isn't always unambiguously the correct answer. In some cases, you might want to share the same dependency among several consumers, like this:
var dep1 = new DependencyOne();
var wd = new WithDependencies(dep1, new DependencyTwo());
var another = AnotherWithDependencies(dep1, new DependencyThree());
In other cases, you might not want to share dependencies, in which case the first option is more correct.
This is just a small glimpse of an entire dimension of DI concerned with Lifetime Management. Many DI Containers can take care of that for you, which is one excellent argument to prefer a DI Container over Poor Man's DI.
Once you start using a DI Container, you should follow the Register Resolve Release pattern when resolving types, letting Auto-wiring take care of the actual composition:
var wd = container.Resolve<WithDependencies>();
The above example assumes that the container is already correctly configured.
If you need to create a dependency which has its own dependencies, you can either A) do it yourself, or B) ask something else to do it for you. Option A negates the benefits of dependency injection (decoupling, etc.), so I would say option B is a better starting point. Now, we have chosen to use the factory pattern, no matter whether it takes the form of a service locator (i.e. IoC.Resolve), a static factory, or an instance factory. The point is that we have delegated that responsibility to an external authority.
There are a number of trade-offs required for static accessors. (I went over them in another answer, so I won't repeat them here.) In order to avoid introducing a dependency on the infrastructure or the container, a solid option is to accept a factory for creating WithDependencies when we need an instance somewhere else:
public class NeedsWithDependencies
{
private readonly IWithDependenciesFactory _withDependenciesFactory;
public NeedsWithDependencies(IWithDependenciesFactory withDependenciesFactory)
{
_withDependenciesFactory = withDependenciesFactory;
}
public void Foo()
{
var withDependencies = _withDependenciesFactory.Create();
...Use the instance...
}
}
Next, we can create a container-specific implementation of the factory:
public class WithDependenciesFactory : IWithDependenciesFactory
{
private readonly IContainer _container;
public WithDependenciesFactory(IContainer container)
{
_container = container
}
public WithDependencies Create()
{
return _container.Resolve<WithDependencies>();
}
}
Now NeedsWithDependencies is completely isolated from any knowledge of how WithDependencies gets created; it also exposes all its dependencies in its constructor, instead of hiding dependencies on static accessors, making it easy to reuse and test.
Defining all those factories can get a little cumbersome, though. I like Autofac's factory relationship type, which will detect parameters of the form Func<TDependency> and automatically inject a function which serves the same purpose as the hand-coded factory above:
public class NeedsWithDependencies
{
private readonly Func<WithDependencies> _withDependenciesFactory;
public NeedsWithDependencies(Func<WithDependencies> withDependenciesFactory)
{
_withDependenciesFactory = withDependenciesFactory;
}
public void Foo()
{
var withDependencies = _withDependenciesFactory();
...Use the instance...
}
}
It also works great with runtime parameters:
public class NeedsWithDependencies
{
private readonly Func<int, WithDependencies> _withDependenciesFactory;
public NeedsWithDependencies(Func<int, WithDependencies> withDependenciesFactory)
{
_withDependenciesFactory = withDependenciesFactory;
}
public void Foo(int x)
{
var withDependencies = _withDependenciesFactory(x);
...Use the instance...
}
}
Sometimes I try to get rid of factories or at least not depend directly on them, so Dependency Injection (without factories) is useful of course.
Therefore I use Google Juice, cause its a small little framework using Java Annotations and you can quickly change your injections / dependencies. Just take a look at it:
http://code.google.com/p/google-guice/
We are trying to figure out how to setup Dependency Injection for situations where service classes can have different dependencies based on how they are used. In our specific case, we have a web app where 95% of the time the connection string is the same for the entire Request (this is a web application), but sometimes it can change.
For example, we might have 2 classes with the following dependencies (simplified version - service actually has 4 dependencies):
public LoginService (IUserRepository userRep)
{
}
public UserRepository (IContext dbContext)
{
}
In our IoC container, most of our dependencies are auto-wired except the Context for which I have something like this (not actual code, it's from memory ... this is StructureMap):
x.ForRequestedType().Use()
.WithCtorArg("connectionString").EqualTo(Session["ConnString"]);
For 95% of our web application, this works perfectly. However, we have some admin-type functions that must operate across thousands of databases (one per client). Basically, we'd want to do this:
public CreateUserList(IList<string> connStrings)
{
foreach (connString in connStrings)
{
//first create dependency graph using new connection string
????
//then call service method on new database
_loginService.GetReportDataForAllUsers();
}
}
My question is: How do we create that new dependency graph for each time through the loop, while maintaining something that can easily be tested?
To defer the creation of an object until runtime, you can use a factory:
public interface ILoginServiceFactory
{
ILoginService CreateLoginService(string connectionString);
}
Usage:
public void CreateUserList(IList<string> connStrings)
{
foreach(connString in connStrings)
{
var loginService = _loginServiceFactory.CreateLoginService(connString);
loginService.GetReportDataForAllUsers();
}
}
Within the loop, do:
container.With("connectionString").EqualTo(connString).GetInstance<ILoginService>()
where "connectionString" is the name of a string constructor parameter on the concrete implementation of ILoginService.
So most UserRepository methods use a single connection string obtained from session, but several methods need to operate against a list of connection strings?
You can solve this problem by promoting the connection string dependency from IContext to the repository and adding two additional dependencies - a context factory and a list of all the possible connections strings the repository might need to do its work:
public UserRepository(IContextFactory contextFactory,
string defaultConnectionString,
List<string> allConnectionStrings)
Then each of its methods can build as many IContext instances as they need:
// In UserRepository
public CreateUserList() {
foreach (string connString in allConnectionStrings) {
IContext context = contextFactory.CreateInstance(connString);
// Build the rest of the dependency graph, etc.
_loginService.GetReportDataForAllUsers();
}
}
public LoginUser() {
IContext context = contextFactory.CreateInstance(defaultConnectionString);
// Build the rest of the dependency graph, etc.
}
We ended up just creating a concrete context and injecting that, then changing creating a wrapper class that changed the context's connection string. Seemed to work fine.
In the C# language, using StructureMap 2.5.4, targeting .NET Framework 3.5 libraries.
I've taken the step to support multiple Profiles in a structure map DI setup, using ServiceLocator model with Bootstrapper activation. First setup was loading default registry, using the scanner.
Now I like to determine runtime what Registry configuration I like to use. Scanning and loading multiple assemblies with registries.
Seems it's not working for the actual implementation (Getting the 202, default instance not found), but a stripped test version does work. The following setup.
Two assemblies containing Registries and implementations
Scanning them in running AppDomain, providing the shared Interface, and requesting Creation Of Instance, using the interfaces in constructor (which get dealt with thanx to the profile on Invokation)
Working code sample below (same structure for other setup, but with more complex stuff, that get's a 202):
What type of couses are possible for a 202, specifically naming the System.Uri type, not being handles by a default type?? (uri makes no sense)
// let structure map create instance of class tester, that provides the registered
// interfaces in the registries to the constructor of tester.
public class Tester<TPOCO>
{
private ITestMe<TPOCO> _tester;
public Tester(ITestMe<TPOCO> some)
{
_tester = some;
}
public string Exec()
{
return _tester.Execute();
}
}
public static class Main {
public void ExecuteDIFunction() {
ObjectFactory.GetInstance<Tester<string>>().Exec();
}
}
public class ImplementedTestMe<TSome> : ITestMe<TSome>
{
public string Execute()
{
return "Special Execution";
}
}
public class RegistryForSpecial : Registry
{
public RegistryForSpecial()
{
CreateProfile("Special",
gc =>
{
gc.For(typeof(ITestMe<>)).UseConcreteType(typeof(ImplementedTestMe<>));
});
}
}
Background articles on Profiles I used.
How to setup named instances using StructureMap profiles?
http://devlicio.us/blogs/derik_whittaker/archive/2009/01/07/setting-up-profiles-in-structuremap-2-5.aspx
http://structuremap.sourceforge.net/RegistryDSL.htm
EDIT:
It seemed the missing interface was actually the one being determined runtime. So here is the next challange (and solved):
I provided a default object whenever StructureMap needs to create the object. Like:
x.ForRequestedType<IConnectionContext>()
.TheDefault.Is.Object(new WebServiceConnection());
This way I got rid of the 202 error, because now a real instance could be used whever structure map needed the type.
Next was the override on runtime. That did not work out at first using the ObjectFactory.Configure method. Instead I used the ObjectFactory.Inject method to overide the default instance. Works like a charm.
ObjectFactory.Inject(typeof(IConnectionContext), context);
Loving the community effort.
Error code 202 means a default instance could not be built for the requested type. Your test code is apparently not equal to your real code that fails. If you are getting an error about Uri, you likely have a dependency that requires a Uri in its constructor. It may not be the class you are asking for - it may be one of that classes dependendencies - or one of the dependencies dependencies... somewhere down the line someone is asking StructureMap to resolve a Uri, which it cannot do, without some help from you.