ViewComponent 无法识别 AspNetCore.Identity“用户”

Question

I'm trying to create a ViewComponent for a series of checkboxes based on this article here:

https://learn.microsoft.com/en-us/as.net/core/mvc/views/view-components?view=as.netcore-2.2

And this SO answer here: https://stackoverflow.com/a/42853705/2300177

Seems like a perfect case scenario for what I'm trying to do. However, I've created my ViewComponent to include Identity UserManager to get the userId :

using BlogPlayground.Data;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Mvc;
using System.Threading.Tasks;

namespace BlogPlayground.ViewComponents
{
    public class LatestArticlesViewComponent : ViewComponent
    {
        private readonly ApplicationDbContext _context;
        private readonly UserManager<IdentityUser> _userManager;


        public LatestArticlesViewComponent(ApplicationDbContext context, UserManager<IdentityUser> userManager)
        {
            _context = context;
            _userManager = userManager;
        }

        public async Task<IViewComponentResult> InvokeAsync()
        {
            string userId = _userManager.GetUserId(User);

            var lastArticles = await _context.Article
                                            .OrderByDescending(a => a.CreatedDate)
                                            .Take(howMany)
                                            .ToListAsync();
            return View(lastArticles);
        }
    }
}

The problem is that when I call this line:

string userId = _userManager.GetUserId(User);

I'm getting an error for User that reads:

cannot convert from 'System.Security.Principal.IPrincipal' to 'System.Security.Claims.ClaimsPrincipal'

This exact code works in all my controllers and I have no idea where the User even comes from. Seems like magic, but I'm guessing somewhere inherent inside Identity? Or did I just miss something included in my controllers? (I searched "User" in my controllers and can't link that to anything.)

I'm using the Pomelo MySQL nuget package if that makes a difference? I wouldn't think so.

Anyone know what I'm missing and how to eliminate this error?

Update: Seems it will work with this (at least it gets rid of the error):

string userId = _userManager.GetUserId(Request.HttpContext.User);

Is that the same thing? Is there a using statement I'm missing? Visual studio (2017) usually clues me in to what I'm missing.

Answer 1

Please make sure you configured services.AddDefaultIdentity and enabled app.UseAuthentication Identity in your Startup .

This is needed to make it available to the app through dependency injection , so you can get it loaded in your LatestArticlesViewComponent .

See the details here: Introduction to Identity on ASP.NET Core

Answer 2

You should use the UserClaimsPrincipal property of ViewComponent instead of the User property, so

string userId = _userManager.GetUserId(UserClaimsPrincipal);