We Keep Coding

Cannot access appsettings.json from class library

I have been following this tutorial in order to get access to my appsettings.json from my MVC project inside my class library.
geek-tutorial
I have a class as such in my class library
using dapper;
public class SqlDataAccess : IConfigManager
{
private readonly IConfiguration _configuration;
public SqlDataAccess(IConfiguration configuration)
{
this._configuration = configuration;
}
public List<T> LoadData<T>(string sql)
{
using (IDbConnection cnn = new SqlConnection(GetConnectionString()))
{
return cnn.Query<T>(sql).ToList();
}
}
public int SaveData<T>(string sql, T data)
{
using (IDbConnection cnn = new SqlConnection(GetConnectionString()))
{
return cnn.Execute(sql, data);
}
}
public string GetConnectionString(string connectionName = "URLShortnerDB")
{
return this._configuration.GetConnectionString(connectionName);
}
}
Interface:
public interface IConfigManager
{
string GetConnectionString(string connectionName);
}
I have added services.AddSingleton<IConfigManager, SqlDataAccess>(); in my mvc startup.cs
However now I would like to use my SqlDataAccess class and call methods from another class e.g:
public static class ShortUrlProcessor
{
public static ShortURLModel GetOriginalURL(string shortUrl)
{
string sql = $#"SELECT * FROM dbo.shorturl WHERE shortUrl = '{ shortUrl }'";
var originalURLEnum = SqlDataAccess.LoadData<ShortURLModel>(sql); //<--- problem
return originalURLEnum.First();
}
}
However SqlDataAccess is not instantiated, and in order to do var _sqldataaccess = SqlDataAccess() I need to pass in a parameter as defined in the constructor of the class. I do not know what to pass in? I do not have any IconfigurationManager in this ShortUrlProcessor class. I understand the reason of doing this is dependancy injection, however I am still not grasping how this all works?

You're very close, but you need to fix a few things. SqlDataAccess implements IConfigManager. Why? What's that providing? Instead, you should have it implement an interface that allows it to expose the functionality other classes depend on.
public interface ISqlDataAccess
{
List<T> LoadData<T>(string sql);
int SaveData<T>(string sql, T data);
}
Change your SqlDataAccess class to implement this interface...
public class SqlDataAccess : ISqlDataAccess
And of course, wire this up with your DI container.
services.AddTransient<ISqlDataAccess, SqlDataAccess>();
Now, any class that needs to run SQL can take a dependency on the ISqlDataAccess interface, utilizing constructor injection to get an instance of ISqlDataAccess. Since we've told the DI container to provide a SqlDataAccess instance when the ISqlDataAccess dependency is present, it will all wire up nicely in your app.
Then we have the issue with ShortUrlProcessor. You declared that class as static. That's bad, because it makes it difficult for it to use constructor injection to get its dependencies, and any other class that needs to invoke its methods has to do so directly, rather than via an abstraction. That violates the Dependency Inversion Principle of SOLID. And since we should always strive to write SOLID code because of the maintainability and testability, we need to fix that.
public class ShortUrlProcessor : IShortUrlProcessor
{
readonly ISqlDataAccess _dataAccess;
public ShortUrlProcessor(ISqlDataAccess dataAccess)
{
_dataAccess = dataAccess;
}
public ShortURLModel GetOriginalURL(string shortUrl)
{
string sql = $#"SELECT * FROM dbo.shorturl WHERE shortUrl = '{ shortUrl }'";
var originalURLEnum = _dataAccess.LoadData<ShortURLModel>(sql); //<--- problem
return originalURLEnum.First();
}
}
And we'll need an interface so other classes don't have to depend directly on ShortUrlProcessor...
public interface IShortUrlProcessor
{
ShortURLModel GetOriginalURL(string shortUrl);
}
And of course, we need to register it with our DI container.
services.AddTransient<IShortUrlProcessor, ShortUrlProcessor>();
Then any class that needs to access the functionality of ShortUrlProcessor can do so via the abstraction IShortUrlProcessor. You mentioned you have a controller calling this, so let's wire that up too.
public class MyController()
{
readonly IShortUrlProcessor _shortUrlProcessor;
public MyController(IShortUrlProcessor shortUrlProcessor)
{
_shortUrlProcessor = shortUrlProcessor;
}
public ActionResult SomeActionMethod()
{
var model = _shortUrlProcessor.GetOriginalURL("asdf");
return View(model);
}
}
We don't have to create an interface for the controller, because the controller will be called by the framework. And we don't have to wire up the controller with the DI container, because the framework handles that for us.
By doing all this, we can easily test individual methods in isolation. There's still some improvements to be made (the SQL Injection attack I mentioned in the comments needs to be fixed), but it's a good step in the right direction.

Simple Injector - Inject service based on the specified generic type at runtime

I was a long time user of Autofac that recently switched to Simple Injector for my DI container needs. When I used Autofac, I was able to do something I'm still not able to do with Simple Injector, maybe because I do not yet perfectly understand the API.
Let's say I have the service IEntityRepository of TEntity and TDbContext. It's implementation looks like that:
public class EntityRepository<TEntity, TDbContext> : IEntityRepository<TEntity, TDbContext>
where TDbContext : IEntityDbContext where TEntity : class
{
public EntityRepository(TDbContext dbContext)
{
}
}
With Autofac, I was able to register the open generic implementation EntityRepository as the open generic interface IEntityRepository, so when I would inject say, IEntityRepository of Product and IProductsDbContext, the DI container would automatically guess that I inject through the constructor an instance of ProductsDbContext.
Is this possible with Simple Injector? I tries these, but it still fails:
container.Register(typeof(IEntityRepository<,>), typeof(EntityRepository<,>).Assembly);
container.Register(typeof(IEntityRepository<,>), typeof(EntityRepository<,>));
Thanks in advance for you help!
EDIT:
So here's a full exemple with Autofac as requested by Steven. Create a new .NET Core Console Application. You'll need to install the NuGet Package Autofac.
Program.cs:
internal class Program
{
private static void Main(string[] args)
{
var builder = new ContainerBuilder();
builder.RegisterType<ProductsDbContext>().AsImplementedInterfaces();
builder.RegisterGeneric(typeof(EntityRepository<,>)).As(typeof(IEntityRepository<,>));
var container = builder.Build();
using (var scope = container.BeginLifetimeScope())
{
var productsRepository = scope.Resolve<IEntityRepository<Product, IProductsDbContext>>();
Console.WriteLine($"Resolved IEntityRepository is of type: {productsRepository.GetType()}");
}
}
}
ProductsDbContext.cs
public class ProductsDbContext : IProductsDbContext
{
public void Dispose()
{
// Demo, do nothing.
}
public int SaveChanges()
{
throw new System.NotImplementedException();
}
}
Product.cs
public class Product
{
public int Id { get; set; }
public string Name { get; set; }
}
EntityRepository.cs
public class EntityRepository<TEntity, TDbContext> : IEntityRepository<TEntity, TDbContext>
where TDbContext : IEntityDbContext where TEntity : class
{
private readonly TDbContext _dbContext;
public EntityRepository(TDbContext dbContext)
{
_dbContext = dbContext;
Console.WriteLine($"Database context is of type {dbContext.GetType()}.");
}
public IQueryable<TEntity> Where(Expression<Func<TEntity, bool>> whereClause)
{
throw new NotImplementedException();
}
}
IEntityDbContext.cs
public interface IEntityDbContext : IDisposable
{
int SaveChanges();
}
IProductsDbContext.cs
public interface IProductsDbContext : IEntityDbContext
{
}
IEntityRepository.cs
public interface IEntityRepository<TEntity, TDbContext> where TDbContext : IEntityDbContext where TEntity : class
{
IQueryable<TEntity> Where(Expression<Func<TEntity, bool>> whereClause);
}
The final console output should ressemble to:
Database context is of type
GenericTypeDiTester.DbContexts.ProductsDbContext. Resolved
IEntityRepository is of type:
GenericTypeDiTester.Repositories.EntityRepository`2[GenericTypeDiTester.Models.Product,GenericTypeDiTester.Interfaces.DbContexts.IProductsDbContext]
You can download the full example there: https://drive.google.com/file/d/1UkIYxLsY6YGwo5jOB5TyyncXc6yho8X5/view?usp=sharing
EDIT 2:
The problem wasn't with the Simple Injector library at the end. It seems that mixing the usage of Microsoft.DependencyInjection and SimpleInjector isn't really a good thing. As suggested by Steven, you should exclusively use SI to register the majority of your services and in rare case, MS.DI (by example for using AddDbContext).
As for my part, I have in my project MediatR, a library that implements the Mediator pattern. This library offers a NuGet package with an extension method AddMediatR for the IServiceCollection of MS.DI, which is supposed to register all handlers properly, but it wasn't the case for me. So I ended up registering the module all by myself using SI.
At the end it everything worked perfectly. You really need to call these lines at the end of the registering process: EnableSimpleInjectorCrossWiring and UseSimpleInjectorAspNetRequestScoping. Nothing else must be registered using the IServiceCollection afterwards. That way, the cross wiring of both DI framework ends up to work beautifully.

The way to register this in Simple Injector is:
container.Register(typeof(IEntityRepository<,>), typeof(EntityRepository<,>));
container.Register<IProductsDbContext, ProductsDbContext>();
There is no AsImplementedInterfaces equivalent in Simple Injector, although there are several ways to achieve rhe same. In the case that ProductsDbContext has multiple interfaces that need to be registered, the most obvious way is to register each interface explicitly:
container.Register<IProductsDbContext, ProductsDbContext>();
container.Register<IUsersDbContext, ProductsDbContext>();
container.Register<ICustomersDbContext, ProductsDbContext>();

Determining which implementation to inject at runtime using .NET Core dependency injection

I have three types of users in my application, let's say Type1, Type2 and Type3.
Then i want to create one service implementation for each type, let's say i have a service to get photos, i would have three services : Type1PhotosService, Type2PhotosService and Type3PhotosService, each of them implementing IPhotosService.
In the web api, i would inject IPhotosService :
IPhotosService _service;
public PhotosController(IPhotosService service){
_service = service;
}
The web api uses token authentication with claims. So what i want to achieve, is for each user, depending on the claim he has : type1 or type2 or type3, the correct implementation of the service will be automatically injected rather than injecting a single service in the startup file.
What i want to avoid, is having one service, with a bunch of switch and if statements to return the correct data depending on user type and the roles he has.
EDIT:
some comments were wondering what's the point of three implementations, so here are more details to give it a little more sense.
The service is a job finder service, and the application has three different profiles : candidate, employer and administration. Each of these profiles need a proper implementation. So rather than having three methods GetCandidateJobs, GetEmployerJobs and GetAdministrationJobs inside the same service and switch on the user type, i preferred to have one implementation per profile type, then depending on the profile type, use the correct implementation.

Without Using a Separate IoC Container
Here's an approach that's way easier than configuring your app to use another IoC container and then configuring that container. After working through this with Windsor this solution seems a whole lot easier.
This approach is simplest if you can use a singleton instance of each service implementation.
We'll start with an interface, some implementations, and the factory we can inject which will return an implementation selected at runtime based on some input.
public interface ICustomService { }
public class CustomServiceOne : ICustomService { }
public class CustomServiceTwo : ICustomService { }
public class CustomServiceThree : ICustomService { }
public interface ICustomServiceFactory
{
ICustomService Create(string input);
}
Here's a really crude implementation of the factory. (Didn't use string constants, or polish it at all.)
public class CustomServiceFactory : ICustomServiceFactory
{
private readonly Dictionary<string, ICustomService> _services
= new Dictionary<string, ICustomService>(StringComparer.OrdinalIgnoreCase);
public CustomServiceFactory(IServiceProvider serviceProvider)
{
_services.Add("TypeOne", serviceProvider.GetService<CustomServiceOne>());
_services.Add("TypeTwo", serviceProvider.GetService<CustomServiceTwo>());
_services.Add("TypeThree", serviceProvider.GetService<CustomServiceThree>());
}
public ICustomService Create(string input)
{
return _services.ContainsKey(input) ? _services[input] : _services["TypeOne"];
}
}
This assumes that you've already registered CustomServiceOne, CustomServiceTwo, etc. with the IServiceCollection. They would not be registered as interface implementations, since that's not how we're resolving them. This class will simply resolve each one and put them in a dictionary so that you can retrieve them by name.
In this case the factory method takes a string, but you could inspect any type or multiple arguments to determine which implementation to return. Even the use of a string as the dictionary key is arbitrary. And, just as an example, I provided fallback behavior to return some default implementation. It might make more sense to throw an exception instead if you can't determine the right implementation to return.
Another alternative, depending on your needs, would be to resolve the implementation within the factory when it's requested. To the extent possible I try to keep most classes stateless so that I can resolve and reuse a single instance.
To register the factory with the IServiceCollection at startup we would do this:
services.AddSingleton<ICustomServiceFactory>(provider =>
new CustomServiceFactory(provider));
The IServiceProvider will be injected into the factory when the factory is resolved, and then the factory will use it to resolve the service.
Here's the corresponding unit tests. The test method is the identical to the one used in the Windsor answer, which "proves" that we can transparently replace one factory implementation with another and change other stuff in the composition root without breaking stuff.
public class Tests
{
private IServiceProvider _serviceProvider;
[SetUp]
public void Setup()
{
var services = new ServiceCollection();
services.AddSingleton<CustomServiceOne>();
services.AddSingleton<CustomServiceTwo>();
services.AddSingleton<CustomServiceThree>();
services.AddSingleton<ICustomServiceFactory>(provider =>
new CustomServiceFactory(provider));
_serviceProvider = services.BuildServiceProvider();
}
[TestCase("TypeOne", typeof(CustomServiceOne))]
[TestCase("TypeTwo", typeof(CustomServiceTwo))]
[TestCase("TYPEThree", typeof(CustomServiceThree))]
[TestCase("unknown", typeof(CustomServiceOne))]
public void FactoryReturnsExpectedService(string input, Type expectedType)
{
var factory = _serviceProvider.GetService<ICustomServiceFactory>();
var service = factory.Create(input);
Assert.IsInstanceOf(expectedType, service);
}
}
As in the Windsor example, this is written to avoid any reference to the container outside of the composition root. If a class depends on ICustomServiceFactory and ICustomService you could switch between this implementation, the Windsor implementation, or any other implementation of the factory.

Using Windsor
I'm going to sidestep the questions about whether or not this makes sense in this case and just attempt to answer the question as asked:
.NET Core's IoC container isn't built particularly well for this sort of scenario. (They acknowledge this in their documentation.) You can work around it by adding another IoC container like Windsor.
The implementation ended up looking way more complicated than I would have liked, but once you get past the setup it's not bad and you get access to Windsor's features. I'm going to provide another answer that doesn't include Windsor. I had to do all of this work to see that I probably like the other approach better.
In your project, add the Castle.Windsor.MsDependencyInjection NuGet package.
Interfaces and Implementations for Testing
For testing, I added some interfaces and implementations:
public interface ICustomService { }
public interface IRegisteredWithServiceCollection { }
public class CustomServiceOne : ICustomService { }
public class CustomServiceTwo : ICustomService { }
public class CustomServiceThree : ICustomService { }
public class RegisteredWithServiceCollection : IRegisteredWithServiceCollection { }
The intent is to create a factory that will select and return an implementation of ICustomService using some runtime input.
Here's an interface which will serve as a factory. This is what we can inject into a class and call at runtime to get an implementation of ICustomService:
public interface ICustomServiceFactory
{
ICustomService Create(string input);
}
Configure the Windsor Container
Next is a class which will configure an IWindsorContainer to resolve dependencies:
public class WindsorConfiguration : IWindsorInstaller
{
public void Install(IWindsorContainer container, IConfigurationStore store)
{
container.AddFacility<TypedFactoryFacility>();
container.Register(
Component.For<ICustomService, CustomServiceOne>().Named("TypeOne"),
Component.For<ICustomService, CustomServiceTwo>().Named("TypeTwo"),
Component.For<ICustomService, CustomServiceThree>().Named("TypeThree"),
Component.For<ICustomService, CustomServiceOne>().IsDefault(),
Component.For<ICustomServiceFactory>().AsFactory(new CustomServiceSelector())
);
}
}
public class CustomServiceSelector : DefaultTypedFactoryComponentSelector
{
public CustomServiceSelector()
: base(fallbackToResolveByTypeIfNameNotFound: true) { }
protected override string GetComponentName(MethodInfo method, object[] arguments)
{
return (string) arguments[0];
}
}
Here's what's going on in here:
The TypedFactoryFacility will enable us to use Windsor's typed factories. It will create an implementation of our factory interface for us.
We're registering three implementations of ICustomService. Because we're registering more than one implementation, each must have a name. When we resolve ICustomService we can specify a name, and it will resolve the type according to that string.
For illustration I registered another implementation of ICustomService without a name. That will enable us to resolve a default implementation if we try to resolve using an unrecognized name. (Some alternatives are just throwing an exception, or returning a "null" instance of ICustomService or creating a class like UnknownCustomService that throws an exception.)
Component.For<ICustomServiceFactory>().AsFactory(new CustomServiceSelector()) tells the container to create a proxy class to implement ICustomServiceFactory. (More on that in their documentation.)
CustomServiceSelector is what takes the argument passed to the factory's Create method and returns the component name (TypeOne, TypeTwo, etc.) that will be used to select a component. In this case we're expecting that the argument passed to the factory will be the same as the registration name we've used. But we could replace this with other logic. Our factory could even take arguments of other types which we could inspect and determine which string to return.
Configure Your App To Use the Windsor Container
Now, in StartUp, modify ConfigureServices to return IServiceProvider instead of void and create an IServiceProvider that combines services registered directly with the IServiceCollection with those registered with the Windsor container:
public IServiceProvider ConfigureServices(IServiceCollection services)
{
services.AddMvc();
var container = new WindsorContainer();
container.Install(new WindsorConfiguration());
return WindsorRegistrationHelper.CreateServiceProvider(container, services);
}
container.Install(new WindsorConfiguration()) allows WindsorConfiguration to configure our container. We could just configure the container right in this method, but this is a nice way to keep our container configurations organized. We can create numerous IWindsorInstaller implementations or our own custom classes to configure the Windsor container.
WindsorRegistrationHelper.CreateServiceProvider(container, services) creates the IServiceProvider that uses container and services.
Does It Work?
I wouldn't post all this without finding out first. Here's some NUnit tests. (I usually write some basic tests for DI configuration.)
The setup creates an IServiceProvider similar to what would happen in the application startup. It creates a container and applies the WindsorConfiguration. I'm also registering a service directly with the ServiceCollection to make sure that the two play well together. Then I'm combining the two into an IServiceProvider.
Then I'm resolving an ICustomerServiceFactory from the IServiceProvider and verifying that it returns the correct implementation of ICustomService for each input string, including the fallback when the string isn't a recognized dependency name.
I'm also verifying that the service registered directly with ServiceCollection is resolved.
public class Tests
{
private IServiceProvider _serviceProvider;
[SetUp]
public void Setup()
{
var services = new ServiceCollection();
services.AddSingleton<IRegisteredWithServiceCollection, RegisteredWithServiceCollection>();
var container = new WindsorContainer();
container.Install(new WindsorConfiguration());
_serviceProvider = WindsorRegistrationHelper.CreateServiceProvider(container, services);
}
[TestCase("TypeOne", typeof(CustomServiceOne))]
[TestCase("TypeTwo", typeof(CustomServiceTwo))]
[TestCase("TYPEThree", typeof(CustomServiceThree))]
[TestCase("unknown", typeof(CustomServiceOne))]
public void FactoryReturnsExpectedService(string input, Type expectedType)
{
var factory = _serviceProvider.GetService<ICustomServiceFactory>();
var service = factory.Create(input);
Assert.IsInstanceOf(expectedType, service);
}
[Test]
public void ServiceProviderReturnsServiceRegisteredWithServiceCollection()
{
var service = _serviceProvider.GetService<IRegisteredWithServiceCollection>();
Assert.IsInstanceOf<RegisteredWithServiceCollection>(service);
}
}
Is All of This Worth It?
Now that I've figured it out, I'd probably use it if I really needed this sort of functionality. It looks worse if you're trying to assimilate both using Windsor with .NET Core and seeing it's abstract factory implementation for the first time. Here's another article with some more information on Windsor's abstract factory without all the noise about .NET Core.

I am going to go out on a limb here and say that the attempt to utilize dependency injection for this purpose is sub-optimal. Normally this would be handled by a Factory pattern that produces service implementations using the dreaded if and switch statements. A simple example is:
public interface IPhotoService {
Photo CreatePhoto(params);
}
public class PhotoServiceFactory {
private readonly IPhotoService _type1;
private readonly IPhotoService _type2;
private readonly IPhotoService _type3;
public PhotoServiceFactory(IDependency1 d1, IDependency2 d2, ...etc) {
_type1 = new ConcreteServiceA(d1);
_type2 = new ConcreteServiceB(d2);
_type3 = new ConcreteServiceC(etc);
}
public IPhotoService Create(User user) {
switch(user.Claim) {
case ClaimEnum.Type1:
return _type1;
case ClaimEnum.Type2:
return _type2;
case ClaimEnum.Type3:
return _type3;
default:
throw new NotImplementedException
}
}
}
Then in your controller:
public class PhotosController {
IPhotoServiceFactory _factory;
public PhotosController(IPhotoServiceFactory factory){
_factory = factory;
}
public IHttpActionResult GetPhoto() {
var photoServiceToUse = _factory.Create(User);
var photo = photoServiceToUse.CreatePhoto(params);
return Ok(photo);
}
}
Alternately just use the concrete classes as arguments in the constructor and follow a similar logic as to the above.

Here is one solution, i have created inside asp.net core console application.
using System;
using System.Collections.Generic;
using Microsoft.Extensions.DependencyInjection;
namespace CreationalPattern
{
class Program
{
static void Main(string[] args)
{
// Add dependency into service collection
var services = new ServiceCollection()
.AddTransient<FordFigoFactory>()
.AddTransient<AudiQ7Factory>();
/* Create CarServiceFactory as singleton because it can be used across the application more frequently*/
services.AddSingleton<ICarServiceFactory>(provider => new CarServiceFactory(provider));
// create a service provider from the service collection
var serviceProvider = services.BuildServiceProvider();
/* instantiate car*/
var factory = serviceProvider.GetService<ICarServiceFactory>();
var audiCar = factory.Create("audi").CreateACar("Blue");
Console.Read();
}
}
public interface ICarServiceFactory
{
ICreateCars Create(string input);
}
public class CarServiceFactory : ICarServiceFactory
{
private readonly Dictionary<string, ICreateCars> _services
= new Dictionary<string, ICreateCars>(StringComparer.OrdinalIgnoreCase);
public CarServiceFactory(IServiceProvider serviceProvider)
{
_services.Add("ford", serviceProvider.GetService<FordFigoFactory>());
_services.Add("audi", serviceProvider.GetService<AudiQ7Factory>());
}
public ICreateCars Create(string input)
{
Console.WriteLine(input + " car is created.");
return _services.ContainsKey(input) ? _services[input] : _services["ford"];
}
}
public interface ICreateCars
{
Car CreateACar(string color);
}
public class FordFigoFactory : ICreateCars
{
public Car CreateACar(string color)
{
Console.WriteLine("FordFigo car is created with color:" + color);
return new Fordigo { Color = color};
}
}
public class AudiQ7Factory : ICreateCars
{
public Car CreateACar(string color)
{
Console.WriteLine("AudiQ7 car is created with color:" + color);
return new AudiQ7 { Color = color };
}
}
public abstract class Car
{
public string Model { get; set; }
public string Color { get; set; }
public string Company { get; set; }
}
public class Fordigo : Car
{
public Fordigo()
{
Model = "Figo";
Company = "Ford";
}
}
public class AudiQ7 : Car
{
public AudiQ7()
{
Model = "Audi";
Company = "Q7";
}
}
}
Explanation:
To understand better try to read the program from bottom to top. We have 3 sections:
Car (Car, Fordigo, AudiQ7)
CarFactory (ICreateCars, FordFigoFactory, AudiQ7Factory)
CarService (ICarServiceFactory, CarServiceFactory)
In this Dependency injection is registered as transient for Factory classes FordFigoFactory and AudiQ7Factory. And Singleton for CarServiceFactory.

Dependency Injection with classes other than a Controller class

At this point I'm injecting things into my Controllers with ease, in some cases building my own ResolverServices class. Life is good.
What I cannot figure out how to do is get the framework to automatically inject into non-controller classes. What does work is having the framework automatically inject into my controller IOptions, which is effectively the configuration for my project:
public class MessageCenterController : Controller
{
private readonly MyOptions _options;
public MessageCenterController(IOptions<MyOptions> options)
{
_options = options.Value;
}
}
I'm thinking whether I can do the same for for my own classes. I assume I'm close when I mimic the controller, like this:
public class MyHelper
{
private readonly ProfileOptions _options;
public MyHelper(IOptions<ProfileOptions> options)
{
_options = options.Value;
}
public bool CheckIt()
{
return _options.SomeBoolValue;
}
}
I think where I'm failing is when I call it like this:
public void DoSomething()
{
var helper = new MyHelper(??????);
if (helper.CheckIt())
{
// Do Something
}
}
The problem I have tracking this down is practically everything that talks about DI is talking about it at the controller level. I tried hunting down where it happens in the Controller object source code, but it gets kinda crazy in there.
I do know I can manually create an instance of IOptions and pass it to the MyHelper constructor, but it seems like I should be able to get the framework do that since it works for Controllers.

Below is a working example of using DI without anything that involves MVC Controllers. This is what I needed to do to understand the process, so maybe it will help somebody else.
The ShoppingCart object gets, via DI, an instance of INotifier (which notifies the customer of their order.)
using Microsoft.Extensions.DependencyInjection;
using System;
namespace DiSample
{
// STEP 1: Define an interface.
/// <summary>
/// Defines how a user is notified.
/// </summary>
public interface INotifier
{
void Send(string from, string to, string subject, string body);
}
// STEP 2: Implement the interface
/// <summary>
/// Implementation of INotifier that notifies users by email.
/// </summary>
public class EmailNotifier : INotifier
{
public void Send(string from, string to, string subject, string body)
{
// TODO: Connect to something that will send an email.
}
}
// STEP 3: Create a class that requires an implementation of the interface.
public class ShoppingCart
{
INotifier _notifier;
public ShoppingCart(INotifier notifier)
{
_notifier = notifier;
}
public void PlaceOrder(string customerEmail, string orderInfo)
{
_notifier.Send("admin#store.com", customerEmail, $"Order Placed", $"Thank you for your order of {orderInfo}");
}
}
public class Program
{
// STEP 4: Create console app to setup DI
static void Main(string[] args)
{
// create service collection
var serviceCollection = new ServiceCollection();
// ConfigureServices(serviceCollection)
serviceCollection.AddTransient<INotifier, EmailNotifier>();
// create service provider
var serviceProvider = serviceCollection.BuildServiceProvider();
// This is where DI magic happens:
var myCart = ActivatorUtilities.CreateInstance<ShoppingCart>(serviceProvider);
myCart.PlaceOrder("customer#home.com", "2 Widgets");
System.Console.Write("Press any key to end.");
System.Console.ReadLine();
}
}
}

Let's say MyHelper is used by MyService which in turn is used by your controller.
The way to resolve this situation is:
Register both MyService and MyHelper in Startup.ConfigureServices.
services.AddTransient<MyService>();
services.AddTransient<MyHelper>();
The controller receives an instance of MyService in its constructor.
public HomeController(MyService service) { ... }
MyService constructor will in turn receive an instance of MyHelper.
public MyService(MyHelper helper) { ... }
The DI framework will be able resolve the whole object graph without problems. If you are worried about new instances being created every time an object is resolved, you can read about the different lifetime and registration options like the singleton or request lifetimes.
You should be really suspicious when you think you have to manually create an instance of some service, as you might end up in the service locator anti-pattern. Better leave creating the objects to the DI Container. If you really find yourself in that situation (let's say you create an abstract factory), then you could use the IServiceProvider directly (Either request an IServiceProvider in your constructor or use the one exposed in the httpContext).
var foo = serviceProvider.GetRequiredService<MyHelper>();
I would recommend reading the specific documentation about the ASP.Net 5 DI framework and about dependency injection in general.

Unfortunately there is no direct way. The only way I managed to make it work is by creating a static class and using that everywhere else as below:
public static class SiteUtils
{
public static string AppName { get; set; }
public static string strConnection { get; set; }
}
Then in your startup class, fill it in as below:
public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
{
//normal as detauls , removed for space
// set my variables all over the site
SiteUtils.strConnection = Configuration.GetConnectionString("DefaultConnection");
SiteUtils.AppName = Configuration.GetValue<string>("AppName");
}
Although this is bad pattern, as this will stay for the whole life cycle of the application and I couldn't find better way to use it outside controller.

Here's a more complete example to directly answer the OP's question, based on the current .NET Core 2.2 DI documentation here. Adding this answer since it may help someone that's new to .NET Core DI, and because this question is Google's top search result.
First, add an interface for MyHelper:
public interface IMyHelper
{
bool CheckIt();
}
Second, update the MyHelper class to implement the interface (in Visual Studio, press ctrl-. to implement the interface):
public class MyHelper : IMyHelper
{
private readonly ProfileOptions _options;
public MyHelper(IOptions<ProfileOptions> options)
{
_options = options.Value;
{
public bool CheckIt()
{
return _options.SomeBoolValue;
}
}
Third, register the interface as a framework-provided service in the DI service container. Do this by registering the IMyHelper service with the concrete type MyHelper in the ConfigureServices method in Startup.cs.
public void ConfigureServices(IServiceCollection services)
{
...
services.AddScoped<IMyHelper, MyHelper>();
...
}
Fourth, create a private variable to reference an instance of the service. Pass the service as an argument in the constructor (via constructor injection) then initialize the variable with the service instance. Reference any properties or call methods on this instance of the custom class via the private variable.
public class MessageCenterController : Controller
{
private readonly MyOptions _options;
private readonly IMyHelper _myHelper;
public MessageCenterController(
IOptions<MyOptions> options,
IMyHelper myHelper
)
{
_options = options.value;
_myHelper = myHelper;
}
public void DoSomething()
{
if (_myHelper.CheckIt())
{
// Do Something
}
}
}

You may use Activator.CreateInstance(). Here is a wrapper function for it. The way you use this is as follows.
var determinedProgrammatically = "My.NameSpace.DemoClass1"; // implements IDemo interface
var obj = CreateInstance<My.NameSpace.IDemo, string>(determinedProgrammatically, "This goes into the parameter of the constructor.", "Omit this parameter if your class lives in the current assembly");
Now you have an instance of obj which is instantiated from type determined programmatically. This obj can be injected into non controller classes.
public TInterface CreateInstance<TInterface, TParameter>(string typeName, TParameter constructorParam, string dllName = null)
{
var type = dllName == null ? System.Type.GetType(typeName) :
System.AppDomain.CurrentDomain.GetAssemblies().FirstOrDefault(a => a.FullName.StartsWith(dllName, System.StringComparison.OrdinalIgnoreCase)).GetType(typeName);
return (TInterface)System.Activator.CreateInstance(type, constructorParam);
}
PS: You may iterate through System.AppDomain.CurrentDomain.GetAssemblies() to determine the name of the assembly that houses your class. This name is used in the 3rd parameter of the wrapper function.

TL;DR: You can save a singleton in a static var and then access it form other classes, but this an anti-pattern, use with caution.
Long version:
As per this question Resolving instances with ASP.NET Core DI from within ConfigureServices
Any services registered in ConfigureServices() can then be injected
into the Configure() method
public void ConfigureServices(IServiceCollection services)
{
services.AddSingleton<FooService>();
}
public void Configure(IApplicationBuilder app, FooService fooService)
{
FooServiceInstance = fooService;
}
public static FooService FooServiceInstance { get; private set; }
And then call it from your other code MyStartupClass.FooService.DoStuff()

Using Ninject to fill Log4Net Dependency

I use Ninject as a DI Container in my application. In order to loosely couple to my logging library, I use an interface like this:
public interface ILogger
{
void Debug(string message);
void Debug(string message, Exception exception);
void Debug(Exception exception);
void Info(string message);
...you get the idea
And my implementation looks like this
public class Log4NetLogger : ILogger
{
private ILog _log;
public Log4NetLogger(ILog log)
{
_log = log;
}
public void Debug(string message)
{
_log.Debug(message);
}
... etc etc
A sample class with a logging dependency
public partial class HomeController
{
private ILogger _logger;
public HomeController(ILogger logger)
{
_logger = logger;
}
When instantiating an instance of Log4Net, you should give it the name of the class for which it will be logging. This is proving to be a challenge with Ninject.
The goal is that when instantiating HomeController, Ninject should instantiate ILog with a "name" of "HomeController"
Here is what I have for config
public class LoggingModule : NinjectModule
{
public override void Load()
{
Bind<ILog>().ToMethod(x => LogManager.GetLogger(GetParentTypeName(x)))
.InSingletonScope();
Bind<ILogger>().To<Log4NetLogger>()
.InSingletonScope();
}
private string GetParentTypeName(IContext context)
{
return context.Request.ParentContext.Request.ParentContext.Request.Service.FullName;
}
}
However the "Name" that is being passed to ILog is not what I'm expecting. I can't figure out any rhyme or reason either, sometimes it's right, most of the time it's not. The Names that I'm seeing are names of OTHER classes which also have dependencies on the ILogger.

I personally have no interest in abstracting away my logger, so my implementation modules reference log4net.dll directly and my constructors request an ILog as desired.
To achieve this, a one line registration using Ninject v3 looks like this at the end of my static void RegisterServices( IKernel kernel ):
kernel.Bind<ILog>().ToMethod( context=>
LogManager.GetLogger( context.Request.Target.Member.ReflectedType ) );
kernel.Get<LogCanary>();
}
class LogCanary
{
public LogCanary(ILog log)
{
log.Debug( "Debug Logging Canary message" );
log.Info( "Logging Canary message" );
}
}
For ease of diagnosing logging issues, I stick the following at the start to get a non-DI driven message too:
public static class NinjectWebCommon
{
public static void Start()
{
LogManager.GetLogger( typeof( NinjectWebCommon ) ).Info( "Start" );
Which yields the following on starting of the app:
<datetime> INFO MeApp.App_Start.NinjectWebCommon - Start
<datetime> DEBUG MeApp.App_Start.NinjectWebCommon+LogCanary - Debug Logging Canary message
<datetime> INFO MeApp.App_Start.NinjectWebCommon+LogCanary - Logging Canary message

The Ninject.Extension.Logging extension already provides all you are implementing yourself. Including support for log4net, NLog and NLog2.
https://github.com/ninject/ninject.extensions.logging
Also you want to use the following as logger type:
context.Request.ParentRequest.ParentRequest.Target.Member.DeclaringType
Otherwise you will get the logger for the service type instead of the implementation type.

The Scope of ILog and ILogger needs to be Transient, otherwise it will just reuse the first logger that it creates. Thanks to #Meryln Morgan-Graham for helping me find that.

Bind<ILog>().ToMethod(x => LogManager.GetLogger(GetParentTypeName(x)))
.InSingletonScope();
You are currently binding in Singleton scope, so only one logger is created which will use the name of the first one created. Instead use InTransientScope()

maybe my answer is late but I'm using this format:
private static void RegisterServices(IKernel kernel)
{
kernel.Bind<ILog>()
.ToMethod(c => LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType))
.InSingletonScope();
}

For all of you that are still looking for the correct answer, the correct implementation is :
public class LoggingModule : NinjectModule
{
public override void Load()
{
Bind<ILog>().ToMethod(x => LogManager.GetLogger(x.Request.Target.Member.DeclaringType));
Bind<ILogger>().To<Log4NetLogger>()
.InSingletonScope();
}
}
Emphasis on:
x.Request.Target.Member.DeclaringType

I do like the idea of wrapping the Log4Net in my own interfaces. I don't want to be dependent on Ninjects implementation, because to me that just means I take a dependency on Ninject throughout my application and I thought that was the exact opposite of what dependency injection is for. Decouple from third party services. So I took the original posters code but I changed the following code to make it work.
private string GetParentTypeName(IContext context)
{
var res = context.Request.ParentRequest.ParentRequest.Service.FullName;
return res.ToString();
}
I have to call ParentRequest.ParentRequest so that when I print the layout %logger it will print the class that calls the Log4Net log method instead of the Log4Net class of the method that called the Log method.