我在使用控制器創(chuàng)建管理員用戶時(shí)遇到問題。這里有什么問題？這是我的代碼：public class ProductsController : Controller{    private SwagExchangeDb db = new SwagExchangeDb();    protected override void Initialize(RequestContext requestContext)    {        var ac  = new ApplicationDbContext();        var userManager = new ApplicationUserManager(new UserStore<ApplicationUser>(ac));        var roleManager = new RoleManager<IdentityRole>(new RoleStore<IdentityRole>(ac));        var user = new ApplicationUser { UserName = "hello@gmail.com", Email = "hello@gmail.com"};        userManager.Create(user, "Hello1234!");        roleManager.Create(new IdentityRole("admin"));        userManager.AddToRole(user.Id, "admin");    }出現(xiàn)錯(cuò)誤：System.InvalidOperationException：'找不到用戶ID。