Having problem with updating IdentityUser - The instance of entity type 'User' cannot be tracked because another instance with the same key value for {'Id'} is already being tracked

Question

User756251838 posted

Hello.

I am using ASP.NET Core 3.1.7 with Identity 3.1.7 and in my current project I didn't use any DTO for creating / updating  User.

and I use the main entity User that derived from IdentityUser.. these codes are for updating the user but i have problem with ChangeTracker.

this is my User Entity.

 public class User : IdentityUser<int>
    {
        public int DepartmentId { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public string NationalCode { get; set; }
        public string Address { get; set; }
        public string IPAddress { get; set; }
        public CorporateTitle CorporateTitle { get; set; }
        public string PhotoPath { get; set; }

        [NotMapped]
        public IFormFile Photo { get; set; }

        [NotMapped]
        public string[] Roles { get; set; }


        public DateTimeOffset DateCreated { get; set; }
        public DateTimeOffset DateModified { get; set; }

        [ForeignKey(nameof(DepartmentId))]
        public Department Department { get; set; }

        public ICollection<UserRole> UserRoles { get; set; }


    }

this block of code is for getting the user and then showing it in view. and its ok and working properly.

 public async Task<IActionResult> EditUser(string id)
        {
            if (!string.IsNullOrEmpty(id))
            {
                var usertoEdit =  await _userRepository.FindByIdAsync(id);
                var userRoles = await _userRepository.GetAllUserRolesAsync(usertoEdit);
                //
                usertoEdit.Roles = userRoles.ToArray();
                //
                if (usertoEdit == null)
                {
                    ViewBag.ErrorMessage = $"some error..";
                    return View("NotFound");
                }

                SelectLists();
                return View(usertoEdit);
            }
            else
            {
                ViewBag.ErrorMessage = $"some error.";
                return View("NotFound");
            }
        }

  [HttpPost]
        [ValidateAntiForgeryToken]
        public async Task<IActionResult> EditUser(User user)
        {
            if (ModelState.IsValid)
            {
               
            
                var editUserResult = await _userRepository.EditUserAsync(user); // here i have problem and after that showing error.

                if (editUserResult.Succeeded)
                {
                    await _userRepository.RemoveAllUserRolesAsync(user);
                    if (user.Roles != null)
                    {
                        await _userRepository.AddRolesToUserAsync(user, user.Roles);
                    }

                    TempData["UserEditedSuccessfully"] = $"some error.";
                    return RedirectToAction(nameof(Index));
                }

                foreach (var error in editUserResult.Errors)
                {
                    ModelState.AddModelError(error.Code, error.Description);
                }

                SelectLists();
                return View(user);

            }
            else
            {
                SelectLists();
                return View(user);
            }
        }

please help me to solve this problem without use any DTO or ViewModel thanks.

Answer 1

User475983607 posted

The error means two different DbContext instances were created.  We see this error a lot when the repository pattern is implemented incorrectly.  The best advice is to drop the repository or generic repository unless you know what you're doing.

Answer 2

User756251838 posted

I just use a normal repository its not generic. and  I test this scenario without any repository, just injected UserManager in controller.. and have the same issue.

( and i just have UserManager in my repository class)

i think the problem is in the post action.

Answer 3

User475983607 posted

i think the problem is in the post action.

Again, this is a very common error that happens when the request has more than one DbContext and the logic uses both.  There can also be a missing await on an async method but that usually causes a threading error.   Also make sure the Dbcontext DI configuration is scope and not transient. 

Answer 4

User756251838 posted

thanks, I solved the problem.

the problem is that when user sent to post action its not attach to ChangeTracker and ChangeTracker Cant specifty that.

_db.Attach(user);

solved with this line of code.