InvalidOperationException：无法解析“Microsoft.AspNetCore.Http.IHttpContextAccessor”类型的服务
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InvalidOperationException: Unable to resolve service for type 'Microsoft.AspNetCore.Http.IHttpContextAccessor'
提问by YuriyP
I started to convert my asp.net core RC1 project to RC2 and faced with problem that now IHttpContextAccessordoes not resolved.
我开始将我的 asp.net core RC1 项目转换为 RC2 并面临现在IHttpContextAccessor没有解决的问题。
For sake of simplicity I created new ASP.NET RC2 project using Visual Studio Template ASP.NET Core Web Application (.Net Framework). Than I added constructor for HomeController which template created for me.
为简单起见，我使用 Visual Studio Template 创建了新的 ASP.NET RC2 项目ASP.NET Core Web Application (.Net Framework)。比我为 HomeController 添加了构造函数，它为我创建了模板。
public HomeController(IHttpContextAccessor accessor)
{
}
And after I start application I receive next error:
在我启动应用程序后，我收到下一个错误：
InvalidOperationException: Unable to resolve service for type 'Microsoft.AspNetCore.Http.IHttpContextAccessor' while attempting to activate 'TestNewCore.Controllers.HomeController'. в Microsoft.Extensions.Internal.ActivatorUtilities.GetService(IServiceProvider sp, Type type, Type requiredBy, Boolean isDefaultParameterRequired)
InvalidOperationException：尝试激活“TestNewCore.Controllers.HomeController”时无法解析“Microsoft.AspNetCore.Http.IHttpContextAccessor”类型的服务。• Microsoft.Extensions.Internal.ActivatorUtilities.GetService(IServiceProvider sp, Type type, Type requiredBy, Boolean isDefaultParameterRequired)
In my real application I need to resolve IHttpContextAccessorin my own service class for getting access to _contextAccessor.HttpContext.Authenticationand to _contextAccessor.HttpContext.User. Everething works fine in RC1. So how can it suppose to be in RC2?
在我的实际应用程序中，我需要IHttpContextAccessor在我自己的服务类中解析以访问_contextAccessor.HttpContext.Authentication和访问_contextAccessor.HttpContext.User. Everething 在 RC1 中运行良好。那么它怎么可能出现在 RC2 中呢？
回答by Joe Audette
IHttpContextAccessor is no longer wired up by default, you have to register it yourself
IHttpContextAccessor 不再默认绑定，需要自己注册
services.TryAddSingleton<IHttpContextAccessor, HttpContextAccessor>();
回答by CalC
As of .NET Core 2.1 there is an extension method that has been added to correctly register an IHttpContextAccessoras a singleton. See Add helper to register IHttpContextAccessor #947. Simply add as follows in your ConfigureServices()method:
从 .NET Core 2.1 开始，添加了一个扩展方法以将 正确注册IHttpContextAccessor为单例。请参阅添加帮助程序以注册 IHttpContextAccessor #947。只需在您的ConfigureServices()方法中添加以下内容：
services.AddHttpContextAccessor();
This is equivalent to:
这相当于：
services.TryAddSingleton<IHttpContextAccessor, HttpContextAccessor>();
