注册MVC5后向用户添加角色

Question

I want to add newly registered user to a "Standard" role in my application. But when I try to register a new user I get an ArgumentNullException on _userManager.AddToRole(user.Id, "Standard");

This is my code

// POST: /Account/Register
        [HttpPost]
        [AllowAnonymous]
        [ValidateAntiForgeryToken]
        public async Task<ActionResult> Register(RegisterViewModel model)
        {
            if (ModelState.IsValid)
            {
                var user = new ApplicationUser { 
                    UserName = model.Email, 
                    Email = model.Email, 
                    PostalCode = model.PostalCode };


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

                if (result.Succeeded)
                {
                    await SignInManager.SignInAsync(user, isPersistent:false, rememberBrowser:false);

                    // For more information on how to enable account confirmation and password reset please visit http://go.microsoft.com/fwlink/?LinkID=320771
                    // Send an email with this link
                    // string code = await UserManager.GenerateEmailConfirmationTokenAsync(user.Id);
                    // var callbackUrl = Url.Action("ConfirmEmail", "Account", new { userId = user.Id, code = code }, protocol: Request.Url.Scheme);
                    // await UserManager.SendEmailAsync(user.Id, "Confirm your account", "Please confirm your account by clicking <a href=\"" + callbackUrl + "\">here</a>");

                    // Gebruiker krijgt een rol toegewezen (0,4)
                    _userManager.AddToRole(user.Id, "Standard");

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

            // If we got this far, something failed, redisplay form
            return View(model);
        }

Answer 1

Don't forget to save your context, this might be the issue that an id is not known yet.

This code is the one I allways use.

_idManager.CreateUser(newUser, model.Password);
await _db.SaveChangesAsync();

_idManager.AddUserToRole(newUser.Id, "Standard");
await _db.SaveChangesAsync();