如何在 ASP.NET Core 1.0 的 DI 中的 Startup 类中添加 IHttpContextAccessor?

How to add IHttpContextAccessor in the Startup class in the DI in ASP.NET Core 1.0?(如何在 ASP.NET Core 1.0 的 DI 中的 Startup 类中添加 IHttpContextAccessor?)

问题描述

在 ASP.NET Core RC 1 中，我使用以下代码检索上下文的值(页面的完整地址).然后我在配置中记录了这个值.

In ASP.NET Core RC 1 I used the following code to retrieve the value of context (full address of the page). Then I recorded this value in the configuration.

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();
        });
        }
   }

现在我开始在 ASP.NET Core 1.0 上更新项目.但在网站启动期间，我收到以下错误:

Now I started to update the project on ASP.NET Core 1.0. But during the launch of the site I get the following error:

System.InvalidOperationException 无法解析类型的服务'Microsoft.AspNetCore.Http.IHttpContextAccessor' 尝试激活MyProject.Startup".

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

在Microsoft.Extensions.Internal.ConstructorMatcher.CreateInstance(IServiceProvider提供者)在Microsoft.Extensions.Internal.ActivatorUtilities.CreateInstance(IServiceProvider提供者，类型 instanceType，Object[] 参数)在Microsoft.Extensions.Internal.ActivatorUtilities.GetServiceOrCreateInstance(IServiceProvider提供者，类型类型)在Microsoft.Extensions.DependencyInjection.ActivatorUtilities.GetServiceOrCreateInstance(IServiceProvider提供者，类型类型)在Microsoft.AspNetCore.Hosting.Internal.StartupLoader.LoadMethods(IServiceProvider服务，类型 startupType，字符串 environmentName)在Microsoft.AspNetCore.Hosting.<>c__DisplayClass1_0.b__1(IServiceProvidersp) 在Microsoft.Extensions.DependencyInjection.ServiceLookup.FactoryService.Invoke(ServiceProvider提供者)在Microsoft.Extensions.DependencyInjection.ScopedCallSite.Invoke(ServiceProvider提供者)在Microsoft.Extensions.DependencyInjection.SingletonCallSite.Invoke(ServiceProvider提供者)在Microsoft.Extensions.DependencyInjection.<>c__DisplayClass12_0.b__0(ServiceProvider提供者)在Microsoft.Extensions.DependencyInjection.ServiceProvider.GetService(类型服务类型)在Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider提供者，类型 serviceType) 在Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider提供者)在Microsoft.AspNetCore.Hosting.Internal.WebHost.EnsureStartup() 在Microsoft.AspNetCore.Hosting.Internal.WebHost.EnsureApplicationServices()在 Microsoft.AspNetCore.Hosting.Internal.WebHost.BuildApplication()

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版本 1.0.0-rtm-21431 |微软视窗 6.1.7601 S

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

应用启动时如何获取新版本的IHttpContextAccessor?

How do I get the new version IHttpContextAccessor during application startup?

推荐答案

不再是默认服务.您必须在 Startup.cs 中配置它

It is no longer a default service. You have to configure it in Startup.cs

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

更新:在 ASP.NET Core 2.1 中，添加了 AddHttpContextAccessor 辅助扩展方法 以正确注册具有正确生命周期(单例)的 IHttpContextAccessor.所以，在 ASP.NET Core 2.1 及以上版本中，代码应该是

UPDATE: In ASP.NET Core 2.1, the AddHttpContextAccessor helper extension method was added to correctly register the IHttpContextAccessor with the correct lifetime (singleton). So, in ASP.NET Core 2.1 and above, the code should be

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

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

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