InvalidOperationException：无法解析类型为'Microsoft.AspNetCore.Identity.UserManager的服务错误

Question

我在帐户控制器中有以下代码

 public sealed class AccountController : Controller
    {
        #region Fields

        private readonly IUserService _userService;

        #endregion

        #region Ctor

        public AccountController(IUserService userService)
        {
            _userService = userService;
        }

        #endregion

        #region Register

        public IActionResult Register()
        {
            return View();
        }

        [HttpPost]
        public async Task<IActionResult> Register(RegisterModel model)
        {
            if (!ModelState.IsValid)
            {
                return View();
            }

            var user = _userService.Register(model);

            var result = await _userService.CreateAsync(user, model.Password);

            if (result)
            {
                await _userService.SignInAsync(user, false);

                return RedirectToAction("Index", "Home");
            }

            return View(model);
        }

我的startup.cs看起来像下面的代码

services.AddDbContext<CourseAppIdentityContext>(options =>
                options.UseSqlServer(Configuration.GetConnectionString("CourseAppIdentityContext"), sqlServerOptions => sqlServerOptions.MigrationsAssembly("Tada.CourseApp.Data")));

            services.AddDefaultIdentity<IdentityUser>()
                .AddRoles<IdentityRole>()
                .AddEntityFrameworkStores<CourseAppIdentityContext>()
                .AddDefaultTokenProviders();

我的UserService看起来像

 public class UserService : IUserService
    {
        private readonly UserManager<IdentityUser> _userManager;
        private readonly SignInManager<IdentityUser> _signInManager;

        public UserService(UserManager<IdentityUser> userManager,
                           SignInManager<IdentityUser> signInManager)
        {
            _userManager = userManager;
            _signInManager = signInManager;
        }

        public async Task<bool> CreateAsync(IdentityUser user, string password)
        {
           var result = await _userManager.CreateAsync(user, password);

            if (result.Succeeded)
            {
                return true;
            }

            return false;
        }

当我运行应用程序并打开注册链接

发生此错误

InvalidOperationException：尝试激活“ Tada.CourseApp.Business.Implementations.UserService”时，无法解析类型为“ Microsoft.AspNetCore.Identity.UserManager`1 [Microsoft.AspNet.Identity.EntityFramework.IdentityUser]”的服务。 / p>

我有这样的DI

services.AddSingleton<IUserService, UserService>();

我该如何解决？

谢谢！