I've an abstract class:
[Configuration]
public abstract class AbstractAddon : IAddon
{
private readonly object configuration;
public AbstractAddon(object configuration)
{
this.configuration = configuration;
}
}
And several implementation of this.
I create a binding by convention as:
public class AddonsModule : Ninject.Modules.NinjectModule
{
public override void Load()
{
this.Bind(b => b.FromAssembliesMatching("*")
.SelectAllClasses()
.InheritedFrom(typeof(UIExtensibility.AbstractAddon))
.BindAllBaseClasses()
.Configure(c => c.InSingletonScope())
);
this.Bind<object>().ToProvider<ConfigurationProvider>().WhenClassHas<UIExtensibility.ConfigurationAttribute>();
}
and ConfigurationProvider is:
private class ConfigurationProvider : IProvider<object>
{
public object Create(IContext context)
{
return "configuration settings";
}
//...
}
Inside the Create method of ConfigurationProvider I thought I might be allowed to access which is the concrete class which is being requested around.
Each concrete class have an attribute PluginInformation I need in order to provide the correct configuration object. However, I don't know how to know which is the concrete class NInject is creating at the moment of the Create method provider is performed. And then, I can't get the PluginInformation attribute I need to link it and provide the correct configuration object.
How could I get access to the concrete class NInject is requesting at the moment of the object provider is performed?
The trouble was that on the first level of the IContext context parameter information, there is only the information according the Type it's providing, in my case: object type.
However IContext comes with the complete parent and plan context. So, at the point of the Create method of the provider is performed, some braches of the resolution are solved, for example: AbstractAddon. Every resolved information is on 'Context' like IContext fields. Moreover, the future steps are on 'Plan' like IContext fields.
So, in order to get the concrete type (inherited classes of AbstractAddon), I need to read the next property: context.Request.ParentContext.Plan.Type.
Related
I have configured my .net-core 2.1 service with a database-context in the start-up method.
services.AddDbContext<DatabaseContext>(options => options.UseSqlServer(Configuration.GetConnectionString(nameof(DatabaseContext))));
Now i could do the following to get my database-context in my controller:
var context = serviceProvider.GetService<DatabaseContext>();
This works very well. But how could i access the Database-Context in a normal class something like this sould be done:
public class MyAccessClass{
public MyAccessClass(){
//Access the ServiceProvider or get the Database-Context class anywhere else
}
}
I don't want to pass the database-context object through the constructor or to initialize the DatbaseContext Class again.
Thanks for your help.
You should take your dependencies through the constructor, preferrably an interface, e.g. IDatabaseContext, but code sample below based on your code. If you add MyAccessClass as a service, e.g. services.AddTransient<MyAccessClass>(), and then use dependency injection in your controller, the database context would be automatically injected in the constructor by the default IoC container in ASP.NET Core.
You shouldn't have it rely on IServiceProvider, the reasoning is that your class wants to make no assumption of implementations, it just needs the database context. Having it rely on IServiceProvider would assume this context, and any possible future dependencies, comes from the IoC in ASP.NET Core which may not be the case (what if you just want to release this as a class library later on?). It would make the MyAccessClass class hard to test and use outside of a controller.
You say in your comment:
"...or get the Database-Context class anywhere else"
That anywhere else is completely flexible by simply accepting the context into the constructor since your class doesn't know where anywhere else is but whatever is creating your class does know!
Example of DI in ASP.NET Core
Take context as a dependency through constructor
public class MyAccessClass{
private readonly DatabaseContext databaseContext;
public MyAccessClass(DatabaseContext databaseContext) {
this.databaseContext = databaseContext;
}
}
Add as service
public void ConfigureServices(IServiceCollection services)
{
services.AddTransient<MyAccessClass>();
}
Inject into a controller
public class MyController : Controller
{
private readonly MyAccessClass myAccessClass;
//Happily injected through DI
public MyController(MyAccessClass myAccessClass)
{
this.myAccessClass = myAccessClass;
}
}
Or inject straight into an action
public class MyController : Controller
{
public MyController()
{
}
public IActionResult MyAction([FromServices] MyAccessClass myAccessClass)
{
}
}
I have an Interface that will take in a generic type T
internal interface IQuestion<T> where T : IWithOptionsId
{
Task<T> Provide(Guid id);
}
Following by that I will implement this interface in multiple classes. For example
public class SomeProvider : IQuestion<OptionsClass>
{
private readonly IRepository _repository;
public SomeProvider(IRepository repository)
{
_repository = repository;
}
public async Task<OptionsClass> Provide(Guid id)
...
}
To register this with outofac I used this
Autofac.RegisterAssemblyTypes(
Assembly.GetExecutingAssembly())
.AsImplementedInterfaces()
.AsClosedTypesOf(typeof(IQuestion<>));
My question is this. I have multiple instances for this interface. How do I access different instance once at the run time? If my IQuestion<T> will take in Options class and also it will take in Answer class how can I get an instance of those classes during run time?
I'm pretty sure you can just inject the instance itself. Not great practice, but it should work:
public SomeClass(SomeProvider<OptionsClass> provider)
You could also try creating a named instance when you register it, and inject that. See this and this.
According COMPOSITION ROOT pattern, I must to construct all dependencies graph as close as possible to the application's entry point.
My architecture is plugin oriented. So, if someone wants to extend my base system he can.
For example, in my base system I have this structure:
View Layer
Services Layer
Data Access Layer
Model Layer
In DAL, I expose some classes like:
IRepository
NHibernateRepository
ProductRepository
So, I'd like if a plugin wants to extend my base Product class to ExtendedProduct, and then create ExtendedProductRepository that inherits from NHibernateRepository.
The question is:
How can instantiate from my base system an instance of NHibernateRepository using NInject?
So, I know the first thing to do is to construct the graph dependencies:
using (var kernel = new StandardKernel())
{
kernel.Bind(b => b.FromAssembliesMatching("*")
.SelectAllClasses()
.InheritedFrom<IRepository>()
.BindAllInterfaces());
}
However, I'm figuring out that when I execute something like:
kernel.GetAll<IRepository>()
It's going to return me a ProductRepository instance, and another ProductExtendedRepository under two IRepository objects.
So, how I can save a ProductExtended object from my base system...?
Another question, would be, how could I inject a object instance in my plugins, or, how can plugins autoinject some instance of base system assembly?
Thanks for all.
I'll appreciate a lot some help.
I use this pattern for my NHibernate based projects:
public interface IRepository<T> : IQueryable<T>
{
T Get(int id);
void Save(T item);
void Delete(T item);
}
public class NHibernateRepository<ModelType> : IRepository<ModelType>
where ModelType : class
{
// implementation
}
then...
public interface IProductRepository : IRepository<Product>
{
// product specific data access methods
}
public class ProductRepository : NHibernateRepository<Product>, IProductRepository
{
// implementation
}
... and in Ninject Module:
Bind(typeof(IRepository<>)).To(typeof(NHibernateRepository<>));
Bind<IProductRepository>().To<ProductRepository>();
then you can either request the base functionality like:
public Constructor(IRepository<Product> repo) { ... }
or specific product repository functionality:
public Constructor(IProductRepository repo) { ... }
your plugins can either get the base functionality and won't have to register anything:
public PluginConstructor(IRepository<ProductExtended> repo { ... }
or create their own repositories and register them in a Ninject module.
Thanks dave.
It's perfect. I'll try it.
However, how could I save or get or update (whichever IRepository methods)... an ExtendedProduct instance from my base system?
Think the follow out:
public interface BasePlugin<T> {...}
In another assembly:
public class PluginExtendedProduct : BasePlugin<ExtendedProduct>
{
public PluginExtendedProduct (IRepository<ExtendedProduct> repo { ... }
}
My headache is how to create an instance of (so, ExtendedProduct) in my base system in order to call methods PluginExtendedProduct that uses an IRepository.
I don't know if I'm explaining myself well...
Thanks for all.
I just recently started using Ninject (v2.2.0.0) in my ASP.NET MVC 3 application. So far I'm thrilled with it, but I ran into a situation I can't seem to figure out.
What I'd like to do is bind an interface to concrete implementations and have Ninject be able to inject the concrete implementation into a constructor using a factory (that will also be registered with Ninject). The problem is that I'd like my constructor to reference the concrete type, not the interface.
Here is an example:
public class SomeInterfaceFactory<T> where T: ISomeInterface, new()
{
public T CreateInstance()
{
// Activation and initialization logic here
}
}
public interface ISomeInterface
{
}
public class SomeImplementationA : ISomeInterface
{
public string PropertyA { get; set; }
}
public class SomeImplementationB : ISomeInterface
{
public string PropertyB { get; set; }
}
public class Foo
{
public Foo(SomeImplementationA implA)
{
Console.WriteLine(implA.PropertyA);
}
}
public class Bar
{
public Bar(SomeImplementationB implB)
{
Console.WriteLine(implB.PropertyB);
}
}
Elsewhere, I'd like to bind using just the interface:
kernel.Bind<Foo>().ToSelf();
kernel.Bind<Bar>().ToSelf();
kernel.Bind(typeof(SomeInterfaceFactory<>)).ToSelf();
kernel.Bind<ISomeInterface>().To ...something that will create and use the factory
Then, when requesting an instance of Foo from Ninject, it would see that one of the constructors parameters implements a bound interface, fetch the factory, and instantiate the correct concrete type (SomeImplementationA) and pass it to Foo's constructor.
The reason behind this is that I will have many implementations of ISomeInterface and I'd prefer to avoid having to bind each one individually. Some of these implementations may not be known at compile time.
I tried using:
kernel.Bind<ISomeInterface>().ToProvider<SomeProvider>();
The provider retrieves the factory based on the requested service type then calls its CreateInstance method, returning the concrete type:
public class SomeProvider : Provider<ISomeInterface>
{
protected override ISomeInterface CreateInstance(IContext context)
{
var factory = context.Kernel.Get(typeof(SomeInterfaceFactory<>)
.MakeGenericType(context.Request.Service));
var method = factory.GetType().GetMethod("CreateInstance");
return (ISomeInterface)method.Invoke();
}
}
However, my provider was never invoked.
I'm curious if Ninject can support this situation and, if so, how I might go about solving this problem.
I hope this is enough information to explain my situation. Please let me know if I should elaborate further.
Thank you!
It seems you have misunderstood how ninject works. In case you create Foo it sees that it requires a SomeImplementationA and will try to create an instance for it. So you need to define a binding for SomeImplementationA and not for ISomeInterface.
Also most likely your implementation breaks the Dependency Inversion Princple because you rely upon concrete instances instead of abstractions.
The solution to register all similar types at once (and the prefered way to configure IoC containers) is to use configuration by conventions. See the Ninject.Extensions.Conventions extenstion.
I have a repository like this:
public class Repository<T> : IRepository<T> where T : class
{
private readonly ISession session;
public Repository(ISession session)
{
this.session = session;
}
}
I use NHQS and I usually do this to get a ISession object:
SessionFactory.For<T>().OpenSession();
How do I setup Ninject to create a session automatically for the requested type and bind it? I tried this but I don't know what to put in the For<>():
kernel.Bind(typeof(IRepository<>))
.To(typeof(Repository<>))
.WithConstructorArgument("session", SessionFactory.For<>().OpenSession());
Looks like I need to get the generic type being used and pass it in the For<>()
How do I do that?
You should'nt use WithConstructorArgument; create a binding for ISession instead.
kernel.Bind<ISession>.ToMethod(context => ....).InRequestScope();
You can get the IRepository<> type from context.Request.ParentRequest.Service. You can now extract the entity type using reflection. However, if you are using the same database for all entities then it is probably easier to return a general session for all repositories.