来自中间件的ASP.NET 5 DI注册

Question

I have a middleware class that gets the current user logged into the application from the database for the current request:

public class CurrentUserMiddleware
{
    RequestDelegate m_next;
    UserManager<User> m_userManager;

    public CurrentUserMiddleware(RequestDelegate next, UserManager<User> userManager )
    {
        m_next = next;
        m_userManager = userManager;
    }

    public async Task Invoke(HttpContext context)
    {
        var userId = context.User.Identity.GetUserId();
        var user = await m_userManager.FindByIdAsync(userId);

        var currentUserContext = new CurrentUserContext { User = user };

        // Register CurrentUserContext with DI to this currentUserContext instance

        await m_next(context);
    }
}

After this is resolved I want to register a CurrentUserContext that can be resolved in other areas of my application via DI.

For example:

public class HomeController : Controller
{
    private readonly CurrentUserContext m_currentUserContext;

    public HomeController(CurrentUserContext currentUserContext)
    {
        m_currentUserContext = currentUserContext;
    }

    public async Task<IActionResult> Index()
    {
        var userName = m_currentUserContext.User.Username;
        return View();
    }
}

How do I properly register this CurrentUserContext ? All other DI registrations are done in Startup ConfigureServices , however that doesn't work for this case since I need to resolve the CurrentUserContext on each request.

Answer 1

Not sure what DI container you using, so a bit generic...

For most DI containers default instantiation is per-invocation, so irrespective where it registered at the moment of instantiation of the object you can access current context. Most containers also provide an option to specify "factory" method instead of just type name - so you can just call your "Invoke" method from such factory.

Note that most containers don't support async resolution, so you can register objects that will give you access to you "user context" asyncronously:

 ICreateUserContext { Task<CurrentUserContext> GetContextAsync();}