Come aggiungere IHttpContextAccessor nella classe Startup nel DI in ASP.NET Core 1.0?

Question

In ASP.NET Core RC 1 ho utilizzato il seguente codice per recuperare il valore del contesto (indirizzo completo della pagina). Quindi ho registrato questo valore nella configurazione.

public class Startup 
{ 
     public IConfigurationRoot Configuration { get; set; } 
     private IHostingEnvironment CurrentEnvironment { get; set; } 
     private IHttpContextAccessor HttpContextAccessor { get; set; } 
     public Startup(IHostingEnvironment env, 
       IHttpContextAccessor httpContextAccessor) 
      {     
       var builder = new ConfigurationBuilder() 
        .SetBasePath(env.ContentRootPath) 
        .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true) 
        .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true); 

       if (env.IsDevelopment()) 
       { 
        builder.AddUserSecrets(); 
       } 
       builder.AddEnvironmentVariables(); 
       Configuration = builder.Build(); 
       CurrentEnvironment = env; 
       HttpContextAccessor = httpContextAccessor; 
      } 
     public void ConfigureServices(IServiceCollection services) 
     { 
     ... 

     services.AddOptions(); 
     services.Configure<WebAppSettings>(configuration); 
     services.Configure<WebAppSettings>(settings => 
     { 
      ... 
      settings.WebRootPath = CurrentEnvironment.WebRootPath; 
      settings.DomainUrl = HttpContextAccessor.HttpContext.Request.Host.ToUriComponent(); 
     }); 
     } 
    } 

Ora ho iniziato ad aggiornare il progetto su ASP.NET Core 1.0. Ma durante il lancio del sito ricevo il seguente errore:

System.InvalidOperationException Unable to resolve service for type 'Microsoft.AspNetCore.Http.IHttpContextAccessor' while attempting to activate 'MyProject.Startup'.

at Microsoft.Extensions.Internal.ConstructorMatcher.CreateInstance(IServiceProvider provider) at Microsoft.Extensions.Internal.ActivatorUtilities.CreateInstance(IServiceProvider provider, Type instanceType, Object[] parameters) at Microsoft.Extensions.Internal.ActivatorUtilities.GetServiceOrCreateInstance(IServiceProvider provider, Type type) at Microsoft.Extensions.DependencyInjection.ActivatorUtilities.GetServiceOrCreateInstance(IServiceProvider provider, Type type) at Microsoft.AspNetCore.Hosting.Internal.StartupLoader.LoadMethods(IServiceProvider services, Type startupType, string environmentName) at Microsoft.AspNetCore.Hosting.<>c__DisplayClass1_0.b__1(IServiceProvider sp) at Microsoft.Extensions.DependencyInjection.ServiceLookup.FactoryService.Invoke(ServiceProvider provider) at Microsoft.Extensions.DependencyInjection.ScopedCallSite.Invoke(ServiceProvider provider) at Microsoft.Extensions.DependencyInjection.SingletonCallSite.Invoke(ServiceProvider provider) at Microsoft.Extensions.DependencyInjection.<>c__DisplayClass12_0.b__0(ServiceProvider provider) at Microsoft.Extensions.DependencyInjection.ServiceProvider.GetService(Type serviceType) at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider, Type serviceType) at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider) at Microsoft.AspNetCore.Hosting.Internal.WebHost.EnsureStartup() at Microsoft.AspNetCore.Hosting.Internal.WebHost.EnsureApplicationServices() at Microsoft.AspNetCore.Hosting.Internal.WebHost.BuildApplication()

.NET Framework X64 v4.0.30319.42000 | Microsoft.AspNetCore.Hosting version 1.0.0-rtm-21431 | Microsoft Windows 6.1.7601 S

Come faccio ad avere la nuova versione IHttpContextAccessor durante l'avvio dell'applicazione?

Answer 1

Non è più un servizio predefinito. È necessario configurarlo in Startup.cs

services.TryAddSingleton<IHttpContextAccessor, HttpContextAccessor>(); 
services.TryAddSingleton<IActionContextAccessor, ActionContextAccessor>(); 

UPDATE: In ASP.NET 2.1 core, the AddHttpContextAccessor helper extension method stato aggiunto al registrare correttamente il IHttpContextAccessor con la durata corretta (Singleton). Così, in ASP.NET core 2.1 e superiori, il codice dovrebbe essere

services.AddHttpContextAccessor(); 
services.TryAddSingleton<IActionContextAccessor, ActionContextAccessor>(); 

Fonte: https://github.com/aspnet/Hosting/issues/793