ActionController.HttpContext 什么时候设置？

Question

我正在尝试实现一个 ASP.NET 核心 MVC 网络应用程序，类似于 Jason Taylor 的 CleanArchitecture design. In the WebUi "layer" I try to implement an abstraction of an IIdentityService in which I want to access the ClaimsPrincipal 与当前 HttpRequest 关联。

在对 github 上的源代码进行一些挖掘之后，我发现 Controller.User 属性源于 ControllerBase.HttpContext? which is derived from ControllerContext which in turn is derived from ActionContext，其中 HttpContext 属性定义为

/// <summary>
/// Gets or sets the <see cref="Http.HttpContext"/> for the current request.
/// </summary>
/// <remarks>
/// The property setter is provided for unit test purposes only.
/// </remarks>
public HttpContext HttpContext
{
    get; set;
}

我在这里进入了死胡同。我假设属性是由一些中间件初始化的（即来自 Microsoft.Identity 的 .AddAuthentication() / .AddAuthorization()），但我想确认这一点，所以我知道如何获得对我服务中的那个对象。

IPrincipal 的其他来源，ClaimsPrincipal 我从中找到

System.Web.HttpContext.Current.User
ClaimsPrincipal.Current
Thread.CurrentPrincipal

IHttpContextAccessor _httpContextAccessor;
var principal = _httpContextAccessor.HttpContext?.User;

使用 IHttpContextAccessor here 的文档，但我无法弄清楚 Controller.User 指向的是哪个。

Answer 1

@JHBonarius 在评论中向正确的方向暗示后，我在 the official documentation

中找到了一个记录案例

Use HttpContext from custom components

For other framework and custom components that require access to HttpContext, the recommended approach is to register a dependency using the built-in Dependency Injection (DI) container. The DI container supplies the IHttpContextAccessor to any classes that declare it as a dependency in their constructors:
var builder = WebApplication.CreateBuilder(args);

builder.Services.AddControllersWithViews();
builder.Services.AddHttpContextAccessor();
builder.Services.AddTransient<IUserRepository, UserRepository>();
In the following example:

UserRepository declares its dependency on IHttpContextAccessor. The dependency is supplied when DI resolves the dependency chain and creates an instance of UserRepository.
public class UserRepository : IUserRepository {
    private readonly IHttpContextAccessor _httpContextAccessor;

    public UserRepository(IHttpContextAccessor httpContextAccessor) =>
        _httpContextAccessor = httpContextAccessor;

    public void LogCurrentUser()
    {
        var username = _httpContextAccessor.HttpContext.User.Identity.Name;

        // ...
    } 
} 

ActionController.HttpContext 什么时候设置？

When is ActionController.HttpContext set?

asp.net-core-mvc

asp.net-core

asp.net-core-identity

Use HttpContext from custom components

In the following example: