Do you know how to manually resolve dependencies in .net core?
Something like
DependencyResolver.Resolve<ISomeService>()
UPDATE
I'm in a class that was not injected, I want to resolve it from the inside, rather than pass variables all over the place
Add your dependency in ConfigureServices as below
public void ConfigureServices(IServiceCollection services){
//AddSingleton or AddTransient based on your requirements
services.AddTransient<ISomeService, ConcreteService>();
}
In your controller or anywhere, add IServiceProvider in the constructor like below:
using Microsoft.Extensions.DependencyInjection;
...
public class HomeController
{
...
public HomeController(IServiceProvider serviceProvider)
{
var service = serviceProvider.GetService<ISomeService>();
}
}
#Shazam, Here are some notes or suggestions based on your comment:
If you can not inject because you might not have a constructor in this class, I woud suggest to add a paramter to your function and pass the resolved dependency from outside
Another Idea is to add a static property and initialize its value in ConfigureServices
For Example:
public static class MyClass
{
public static ISomeService MyServiceObj { set; get; }
....
}
In your ConfigureServices
public void ConfigureServices(IServiceCollection services){
services.AddTransient<ISomeService, ConcreteService>();
MyClass.MyServiceObj = services.GetService<ISomeService>();
}
Hope this helps, please rate my answer or leave me a comment if you still in doubt how to do it
Related
I've followed several methods on StackOverflow to fix my issue, none with a result:
My DefaultConnection-string is in my AppSettings.json. To retrieve info I am reading to use the IConfiguration from my startup.cs. The constructor of my MsSQL-context is still asking for this IConfiguration. Note: I'm using a repository pattern.
startup.cs:
public Startup(IConfiguration configuration)
{
this.Configuration = configuration;
}
public IConfiguration Configuration { get; private set; }
public void ConfigureServices(IServiceCollection services)
{
services.AddSingleton<IConfiguration>(Configuration);
I've added the Singleton in my startup after a suggestion. With or without this the constructor of MsSQLContext is still requesting this as a variable to be passed. Leaving the constructor without this gives me the error: Connectionstring not initialized.
AdminMsSQLContext:
private readonly string _connectionString;
public MSSQLAdminContext(IConfiguration configuration)
{
_connectionString = configuration.GetConnectionString("DefaultConnection");
}
Injecting IConfiguration is actually an anti-pattern, anyways. What you should be doing is supplying an action to your scope registration and change your MSSQLAdminContext class to accept just the connection string in its constructor:
public MSSQLAdminContext(string connectionString)
{
_connectionString = connectionString ?? throw new ArgumentNullException(nameof(connectionString));
}
Then:
services.AddScoped(_ =>
new MSSQLAdminContext(Configuration.GetConnectionString("DefaultConnection)));
Your repo should not have knowledge of something like your configuration. If it needs a connection string, then it should take the connection string, and that is all.
I believe the issue you are having is that you have not registered the MSSQLAdminContext with the DI container. Because of this the DI engine does not know to inject the IConfiguration into the class. In your start up you will register this class however you need, I tend to use scoped for these types of classes you may use in multiple places. So something like this.
public void ConfigureServices(IServiceCollection services)
{
services.AddScoped<MSSQLAdminContext>();
services.AddSingleton<IConfiguration>(Configuration);
}
I have a problem with the Automapper on my website and I can't find a solution.
I've created a class called AutoMapperProfile where I'd like to put all my Maps
public class AutoMapperProfile: Profile
{
private readonly IConfiguration _mapper;
public AutoMapperProfile(IConfiguration mapper)
{
_mapper = mapper;
}
protected override void Configure()
{
base.Configure();
_mapper.CreateMap<SlideDTO, Slide>();
_mapper.CreateMap<Slide, SlideDTO>();
}
}
For DI purposes I'm using Ninject, so I've added the following bindings in NinjectWebCommon:
kernel.Bind<IMappingEngine>().ToMethod(ctx => Mapper.Engine);
kernel.Bind<IConfigurationProvider>().ToMethod(x => Mapper.Engine.ConfigurationProvider);
The controller looks like this:
private readonly ISlideRepository slideRepository;
private readonly IMappingEngine mappingEngine;
public HomeController(
ISlideRepository slideRepository,
IMappingEngine mappingEngine)
{
this.slideRepository = slideRepository;
this.mappingEngine = mappingEngine;
}
[HttpGet]
public ActionResult Index()
{
var model = new IndexViewModel();
var slide = slideRepository.GetSlide();
model.Slide = mappingEngine.Map<SlideDTO, Slide>(slide);
return View(model);
}
When I map from SlideDTO to Slide I get the following error:
Missing type map configuration or unsupported mapping.
So my best guess is that I didn't do the binds correctly so that Automapper can see my maps, but I'm not sure how can I fix it.
You don't need to inject IConfiguration into AutoMapperProfile, it already inherits a CreateMap method from Profile.
Make sure that AutoMapperProfile has a parameterless constructor like this:
public class AutoMapperProfile : Profile
{
protected override void Configure()
{
this.CreateMap<SlideDTO, Slide>();
this.CreateMap<Slide, SlideDTO>();
}
}
And then you need to make sure that AutoMapper knows about this profile, here is how you can do it:
Mapper.Engine.ConfigurationProvider.AddProfile<AutoMapperProfile>();
Please note that you can invoke the AddProfile method on any IConfigurationProvider (if you decide not to use the global ConfigurationProvider and Engine).
I am playing with ASP.NET 5. I am trying to understand the new configuration model. I have read several articles. However, I am still unsuccessful in loading a configuration setting. My config.json file looks like this:
{
"App" : {
"Info" : {
"Version":"1.0.0",
"ReleaseDate":"03-15-2015"
}
}
}
My Startup.cs file looks like this:
public class Startup
{
public IConfiguration Configuration { get; private set; }
public Startup()
{
Configuration = new Configuration()
.AddJsonFile("config.json");
}
public void ConfigureServices(IServiceCollection services)
{
services.AddMvc();
}
public void Configure(IApplicationBuilder app)
{
app.UseErrorPage();
app.UseMvc(routes =>
{
routes.MapRoute("default", "{controller}/{action}/{id}", defaults: new { controller = "Home", action = "Index" });
});
app.UseMvc();
app.UseWelcomePage();
}
}
In one of my controllers, I have the following
MyController.cs
using System;
using Microsoft.AspNet.Mvc;
namespace MyOrg.MyApp
{
public class MyController : Controller
{
[HttpGet()]
public ActionResult Index()
{
var version = Configuration.Get("App:Info:Version");
return new HttpStatusCodeResult(200);
}
}
}
When I start the app, I get an error that says:
error CS0103: The name 'Configuration' does not exist in the current context
at Microsoft.Framework.Runtime.Roslyn.RoslynProjectReference.Load(IAssemblyLo
adContext loadContext)
at Microsoft.Framework.Runtime.Loader.ProjectAssemblyLoader.Load(String name,
IAssemblyLoadContext loadContext)
at Microsoft.Framework.Runtime.Loader.ProjectAssemblyLoader.Load(String name)
at kre.host.LoaderContainer.Load(String name)
at kre.hosting.RuntimeBootstrapper.<>c__DisplayClass6_0.<ExecuteAsync>b__4(As
semblyName assemblyName)
at kre.hosting.RuntimeBootstrapper.<>c__DisplayClass6_0.<ExecuteAsync>b__7(Ob
ject sender, ResolveEventArgs a)
at System.AppDomain.OnAssemblyResolveEvent(RuntimeAssembly assembly, String assemblyFullName)
What am I doing wrong? I feel like I've followed the examples I've seen. Yet, I can figure out what I'm doing wrong.
Clearly you want to access Configuration property in your Startup class. And the error method says it doesn't know what Configuration is. So you need a using statement or a fully qualified name. Also, you should avoid naming things the same thing as stuff found in the framework. Your Startup class has a Configuration property, but it also tries to use the Configuration class from Microsoft.Framework.ConfigurationModel. How confusing is that?
Your Configure() method in Startup needs a using statement or fully qualified name so it knows what the Configuration class is.
using Microsoft.Framework.ConfigurationModel; //at the top of your class
Configuration = new Configuration(); //later in the code, we can access without fully qualifying name
or
Configuration = new Microsoft.Framework.ConfigurationModel.Configuration();
In your controller, you may have a similar issue. Replace MyOrg.MyApp.Startup in the example below with whatever the namespace is for your Startup class.
using MyOrg.MyApp.Startup //at the top of your class
Startup.Configuration.Get("App:Info:Version"); //later in the code, we can access without fully qualifying name
or
MyOrg.MyApp.Startup.Startup.Configuration.Get("App:Info:Version");
Better way of doing things
That should be enough to get you started. However, accessing the Startup class to retrieve your configuration isn't ideal, because now your controller's action methods depend on having the Startup class there. That's not very unit testable. Ideally your controllers should be isolated from each other. You should define some sort of interface to hold the configuration info you want, then have the controller depend on that interface. When you're in your site, you'll respond with a class specific to the site's configuration. When unit testing, you can have tight control over the test values by using a different class.
interface ISiteConfig
{
string Version {get; set;}
DateTime ReleaseDate {get; set;}
}
public class SiteConfig : ISiteConfig
{
public string Version {get; set;}
public DateTime ReleaseDate {get; set;}
public SiteConfig()
{
var c = new Configuration()
.AddJsonFile("config.json");
Version = c.Get("App:Info:Version");
ReleaseDate = c.Get("App:Info:ReleaseDate"); //may need to parse here
}
}
public class TestConfig : ISiteConfig
{
public string Version {get; set;}
public DateTime ReleaseDate {get; set;}
public TestConfig(string version, DateTime releaseDate)
{
Version = version;
ReleaseDate = releaseDate;
}
}
Then you'd use Dependency Injection to inject instances of your configuration into the Controller.
public class MyController : Controller
{
private readonly ISiteConfig Config;
public MyController(ISiteConfig config)
{
Config = config;
}
[HttpGet()]
public HttpStatusCodeResult Index()
{
var version = Config.Version;
return new HttpStatusCodeResult(200);
}
}
public class Startup
{
public void Configure(IBuilder app)
{
...
app.UseServices(services =>
{
...
// Set up the dependencies
services.AddTransient<ISiteConfig, SiteConfig>();
...
});
...
}
}
Now you can more easily unit test your action methods, because your unit tests can use the TestConfig class while the site can use the SiteConfig class. And also if you want to change how your configuration is done, you don't have to replace strings in a bunch of different places. You'll have one class where you do so, the rest is strongly typed and easy to change without blowing up your application.
Your unit test might look like this:
//Arrange
var testConfig = new TestConfig("1.0", DateTime.Now );
var controller = new MyController(testConfig );
//Act
var response = controller.Index();
//Assert
Assert.AreEqual(200, response.StatusCode);
As of Beta 5 the accepted answer is no longer correct. There is no longer a Get method on IConfiguration. Also the way of constructing the configuration object is also changed.
The following code works on Beta 7:
// showing using statements here since this is new from Beta 5
using Microsoft.Dnx.Runtime; // renamed was Microsoft.Framework.Runtime
using Microsoft.Framework.Configuration; // renamed was Microsoft.Framework.ConfigurationModel
// other using statements here
// Startup constructor. Note: now takes IApplicationEnvironment
// this is required in order to get base path
public Startup(IHostingEnvironment env, IApplicationEnvironment appEnv)
{
// Setup configuration sources.
var builder = new ConfigurationBuilder(appEnv.ApplicationBasePath)
.AddJsonFile("config.json")
.AddJsonFile("dbconfig.json")
.AddEnvironmentVariables();
Configuration = builder.Build();
}
// property to hold configuration object created in constructor
public IConfiguration Configuration { get; set; }
public void ConfigureServices(IServiceCollection services)
{
// this will bind to an IOptions<AppSettings> instance
// where AppSettings is a class you define that has a set of
// properties that match your configuration section loaded from the
// json file
services.Configure<AppSettings>(Configuration.GetSection("AppSettings"));
// here I am loading a connection string from a json file and passing into an
// new EF 6.x DB Context class
services.AddInstance<TalentAgencyContainer>(new TalentAgencyContainer(Configuration["ConnectionStrings:TalentAgencyContainer"]));
// Add MVC services to the services container.
services.AddMvc();
}
I'm using SignalR 0.5.2 and I'm trying to get a DependencyResolver set up using Unity. I've written the simplest code I can. I have a hub that I'm trying to inject into which looks like this:
public class SimpleHub : Hub
{
private readonly ITestService _service;
public SimpleHub(ITestService service)
{
_service = service;
}
public void Update()
{
Clients.callback("Kevin");
}
}
and a DependencyResolver that looks like this:
public class UnityDependencyResolver : DefaultDependencyResolver
{
private readonly IUnityContainer _container;
public UnityDependencyResolver(IUnityContainer container)
{
_container = container;
}
public override object GetService(Type serviceType)
{
if (_container.IsRegistered(serviceType))
{
return _container.Resolve(serviceType);
}
return base.GetService(serviceType);
}
public override IEnumerable<object> GetServices(Type serviceType)
{
if (_container.IsRegistered(serviceType))
{
return _container.ResolveAll(serviceType);
}
return base.GetServices(serviceType);
}
}
I register the dependency resolver in Global.asax
protected void Application_Start()
{
IUnityContainer container = new UnityContainer();
InitializeContainer(container);
SignalR.IDependencyResolver resolver = new UnityDependencyResolver(container);
GlobalHost.DependencyResolver = resolver;
RouteTable.Routes.MapHubs();
// more MVC stuff here
}
where InitializeContainer register the ITestService in Unity
The resolver "works" in that it's getting called for all the SignalR types, and if I leave my hub with a default constructor it all gets loaded. However the resolver never gets asked to resolve the ITestService interface.
I've also tried passing the resolver to MapHubs, still no luck. I've also tried property injection using the [Dependency] attribute and that didn't work either.
Do I need to register the resolver with MVC as well? (I have tried that by implementing both IDependecyResolver interfaces but get an exception telling me the resolver doesn't implement IServiceLocator)
So I've sort of fixed this. I wondered if the fact that the Hub was registered with the signalr container and the interface was registered with the Unity container was causing the issue. So I registered the Hub with Unity and then everything works.
This sort of makes sense as there are two containers.
Is this the standard behaviour?
In case someone else is wondering... I found a good SPA example that uses
SignalR 1.0.1
Unity 3
A bunch of other frameworks
The interesting thing is the way he create the container, the dependencies and everything else. Worth checking it out.
OK, so I've been working on this for hours. I've found a couple of posts here, but nothing that actually resolves the problem. So, let me try it again...
I have an MVC2 app using Ninject and a custom membership provider.
If I try and inject the provider using the ctor, I get an error: 'No parameterless constructor defined for this object.'
public class MyMembershipProvider : MembershipProvider
{
IMyRepository _repository;
public MyMembershipProvider(IMyRepository repository)
{
_repository = repository;
}
I've also been playing around with factories and Initialize(), but everything is coming up blanks.
Any thoughts/examples?
The Membership provider model can only instantiate a configured provider when it has a default constructor. You might try this using the Service Locator pattern, instead of using Dependency Injection. Example:
public class MyMembershipProvider : MembershipProvider
{
IMyRepository _repository;
public MyMembershipProvider()
{
// This example uses the Common Service Locator as IoC facade, but
// you can change this to call NInject directly if you wish.
_repository = ServiceLocator.Current.GetInstance<IMyRepository>;
}
This is how I was able to do this:
1) I created a static helper class for Ninject
public static class NinjectHelper
{
public static readonly IKernel Kernel = new StandardKernel(new FooServices());
private class FooServices : NinjectModule
{
public override void Load()
{
Bind<IFooRepository>()
.To<EntityFooRepository>()
.WithConstructorArgument("connectionString",
ConfigurationManager.ConnectionStrings["FooDb"].ConnectionString);
}
}
}
2) Here is my Membership override:
public class FooMembershipProvider : MembershipProvider
{
private IFooRepository _FooRepository;
public FooMembershipProvider()
{
NinjectHelper.Kernel.Inject(this);
}
[Inject]
public IFooRepository Repository
{
set
{
_FooRepository = value;
}
}
...
With this approach it doesn't really matter when the Membership provider is instantiated.
I had the same problem at the exact same spot in the book. It wasn't until later on in the book that I noticed there were two separate web.config files. I initially placed my connectionString key in the wrong web.config file. It wasn't until I placed the connectionString in the correct web.config file that the 'no parameterless constructor' error went away.