How to get an instance of IServiceProvider in .NET Core?

IServiceProvider is an interface with single method:

object GetService(Type serviceType);

It's used to create instances of types registered in .NET Core native DI container.

An instance of IServiceProvider itself can be obtained by calling a BuildServiceProvider method of an IServiceCollection. IServiceCollection is a parameter of ConfigureServices method in a Startup class. It seems to be magically called with an instance of IServiceCollection by the framework.

I want to create an instance of IServiceProvider without having Setup method at all. I need it to resolve dependencies in an integration test assembly. Is it possible to get it at all in this scenario?

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最佳答案

This is the default implementation of IServiceCollection from Microsoft: https://github.com/aspnet/DependencyInjection/blob/master/src/DI/ServiceCollection.cs

Looking at the code then you should be able to get an IServiceCollection simply by calling:

var serviceCollection = new Microsoft.Extensions.DependencyInjection.ServiceCollection();

Hope that helps :)

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As goaty mentioned it's enough to create new ServiceCollection. Here's example class which can be used to access DI container in .NET Core:

public static class ServiceProviderFactory
{
public static IServiceProvider ServiceProvider { get; }


static ServiceProviderFactory()
{
HostingEnvironment env = new HostingEnvironment();
env.ContentRootPath = Directory.GetCurrentDirectory();
env.EnvironmentName = "Development";


Startup startup = new Startup(env);
ServiceCollection sc = new ServiceCollection();
startup.ConfigureServices(sc);
ServiceProvider = sc.BuildServiceProvider();
}
}

Startup class is taken from tested project so the service registrations don't need to be repeated.

Then in test class simply use:

var foo = ServiceProviderFactory.ServiceProvider.GetServices(typeof(IFoo));
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First you need to install the Microsoft.Extensions.DependencyInjection NuGet package. (docs, API, API)

Then you create a new ServiceCollection and method chain it with the BuildServiceProvider method. In between that you can also register any service providers.

var serviceProvider = new ServiceCollection()
.AddSingleton<IFooService, FooService>()
.BuildServiceProvider();
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Here is an updated approach:

var host = Host.CreateDefaultBuilder().ConfigureWebHostDefaults(builder =>
{
builder.ConfigureAppConfiguration((hostingContext, config) =>
{
var env = hostingContext.HostingEnvironment;
env.ContentRootPath = Directory.GetCurrentDirectory();
env.EnvironmentName = "Development";
});


builder.UseStartup<Startup>();
}).Build();

Example usage:

host.Services.GetService<IFoo>();
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You can find it in Program.cs

public static IServiceProvider ServiceProvider { get; private set; }


public static void Main(string[] args)
{
IHost build = CreateHostBuilder(args).Build();
ServiceProvider = build.Services;
build.Run();
}
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To get access to existing DI of ASP.NET Core application e.g. in some controller, you should just resolve it in a constructor. Example with some manager and workers:

public IServiceProvider ConfigureServices(IServiceCollection services)
{
services.AddMvc();


services.AddSingleton<IFooManager, FooManager>();
services.AddTransient<IFooWorker, FooWorker>();
}

Manually resolve workers for manager:

public class FooManager: IFooManager
{
private readonly IServiceProvider _serviceProvider;


public FooManager(IServiceProvider serviceProvider)
{
_serviceProvider = serviceProvider;
}


public void Start()
{
var w1 = _serviceProvider.GetRequiredService<IFooWorker>();  // new instance of FooWorker
var w2 = _serviceProvider.GetRequiredService<IFooWorker>();  // new instance of FooWorker
}
}
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use this ServiceProviderA = new ServiceCollection(). . . . . .BuildServiceProvider() .GetRequiredService<IServiceProvider>(); this ServiceProviderA contain itself


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