Question

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。

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。但在网站发布期间，我收到以下错误：

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

在   Microsoft.Extensions.Internal.ConstructorMatcher.CreateInstance（的IServiceProvider   提供者）   Microsoft.Extensions.Internal.ActivatorUtilities.CreateInstance（的IServiceProvider   provider，Type instanceType，Object [] parameters）at   Microsoft.Extensions.Internal.ActivatorUtilities.GetServiceOrCreateInstance（的IServiceProvider   提供者，类型类型）at   Microsoft.Extensions.DependencyInjection.ActivatorUtilities.GetServiceOrCreateInstance（的IServiceProvider   提供者，类型类型）at   Microsoft.AspNetCore.Hosting.Internal.StartupLoader.LoadMethods（的IServiceProvider   services，类型startupType，string environmentName）at   。Microsoft.AspNetCore.Hosting＆LT;＆GT; c__DisplayClass1_0.b__1（的IServiceProvider   sp）at   Microsoft.Extensions.DependencyInjection.ServiceLookup.FactoryService.Invoke（的ServiceProvider   提供者）   Microsoft.Extensions.DependencyInjection.ScopedCallSite.Invoke（的ServiceProvider   提供者）   Microsoft.Extensions.DependencyInjection.SingletonCallSite.Invoke（的ServiceProvider   提供者）   Microsoft.Extensions.DependencyInjection＆LT;＆GT; c__DisplayClass12_0.b__0（的ServiceProvider   提供者）   Microsoft.Extensions.DependencyInjection.ServiceProvider.GetService（类型   serviceType）at   Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService（的IServiceProvider   provider，输入serviceType）at   Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService（的IServiceProvider   提供者）   Microsoft.AspNetCore.Hosting.Internal.WebHost.EnsureStartup（）at   Microsoft.AspNetCore.Hosting.Internal.WebHost.EnsureApplicationServices（）   在Microsoft.AspNetCore.Hosting.Internal.WebHost.BuildApplication（）

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

如何在应用程序启动期间获取新版本的IHttpContextAccessor？

Answer 1

它不再是默认服务。您必须在Startup.cs中配置它

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

更新：在ASP.NET Core 2.1中，添加了the AddHttpContextAccessor helper extension method以正确注册具有正确生命周期的IHttpContextAccessor（单例）。因此，在ASP.NET Core 2.1及更高版本中，代码应为

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

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

Answer 2

您可以通过这种方式添加。

services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();

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

2 个答案: