IServiceProvider in ASP.NET Core

Question

I starting to learn changes in ASP.NET 5(vNext) and cannot find how to get IServiceProvider, for example in "Model"'s method

public class Entity 
{
     public void DoSomething()
     { 
           var dbContext = ServiceContainer.GetService<DataContext>(); //Where is ServiceContainer or something like that ?
     }
}

I know, we configuring services at startup, but where all service collection staying or IServiceProvider?

Answer 1

You have to bring in Microsoft.Extensions.DependencyInjection namespace to gain access to the generic

GetService<T>();

extension method that should be used on

IServiceProvider 

Also note that you can directly inject services into controllers in ASP.NET 5. See below example.

public interface ISomeService
{
    string ServiceValue { get; set; }
}

public class ServiceImplementation : ISomeService
{
    public ServiceImplementation()
    {
        ServiceValue = "Injected from Startup";
    }

    public string ServiceValue { get; set; }
}

Startup.cs

public void ConfigureService(IServiceCollection services)
{
    ...
    services.AddSingleton<ISomeService, ServiceImplementation>();
}

HomeController

using Microsoft.Extensions.DependencyInjection;
...
public IServiceProvider Provider { get; set; }
public ISomeService InjectedService { get; set; }

public HomeController(IServiceProvider provider, ISomeService injectedService)
{
    Provider = provider;
    InjectedService = Provider.GetService<ISomeService>();
}

Either approach can be used to get access to the service. Additional service extensions for Startup.cs

AddInstance<IService>(new Service())

A single instance is given all the time. You are responsible for initial object creation.

AddSingleton<IService, Service>()

A single instance is created and it acts like a singleton.

AddTransient<IService, Service>()

A new instance is created every time it is injected.

AddScoped<IService, Service>()

A single instance is created inside of the current HTTP Request scope. It is equivalent to Singleton in the current scope context.

Updated 18 October 2018

See: aspnet GitHub - ServiceCollectionServiceExtensions.cs

Answer 2

I don't think it is a good idea for an entity (or a model) to have access to any service.

Controllers, on the other hand, do have access to any registered service in their constructors, and you don't have to worry about it.

public class NotifyController : Controller
{
    private static IEmailSender emailSender = null;
    protected static ISessionService session = null;
    protected static IMyContext dbContext = null;
    protected static IHostingEnvironment hostingEnvironment = null;

    public NotifyController(
                IEmailSender mailSenderService,
                IMyContext context,
                IHostingEnvironment env,
                ISessionService sessionContext)
    {
        emailSender = mailSenderService;
        dbContext = context;
        hostingEnvironment = env;
        session = sessionContext;
    }
}