A second operation was started on this context instance before a previous operation completed

Question

Error text: InvalidOperationException: A second operation was started on this context instance before a previous operation completed. This is usually caused by different threads concurrently using the same instance of DbContext. For more information on how to avoid threading issues with DbContext, see https://go.microsoft.com/fwlink/?linkid=2097913. Code:

DI

builder.Services.AddDbContext<MedicardDbContext>(options =>
{
    options.UseSqlServer(builder.Configuration.GetConnectionString("DefaultConnection"));

});
builder.Services.AddScoped(typeof(IGenericRepository<>), typeof(GenericRepository<>));
builder.Services.AddTransient<IUnitOfWork, UnitOfWork>();

Controller:

  public async Task<IActionResult> AllChats()
        {
            var currentUser = await _userManager.GetUserAsync(User);
            var allUsers = await _chatService.GetAllTargetUsersBasedOnRole(currentUser);

            var chatsViewModel = await _chatService.GetListChats(allUsers, currentUser);

            return View(chatsViewModel);
        }

ChatService:

public async Task<List<ChatViewModel>> GetListChats(List<User> allUsers, User currentUser)
        {
            var chatsViewModel = new List<ChatViewModel>();

            foreach (var targetUser in allUsers)
            {
                var chat = new ChatViewModel
                {
                    UserName = targetUser.UserName,
                    FullName = targetUser.ToString(),
                };

                var picture = await GetPictureForChat(targetUser);

                if (picture == null)
                {
                    var doctor = _unitOfWork.GenericRepository<Doctor>().GetAll(doctor => doctor.UserId == targetUser.Id).FirstOrDefault();
                    chat.Picture = doctor.DoctorPicture;
                }
                else
                {
                    chat.Picture = picture;
                }
                chatsViewModel.Add(chat);
            }

            return chatsViewModel;
        }

Method GetPictureForChat:

private async Task<string> GetPictureForChat(User user)
        {
            return await _userManager.IsInRoleAsync(user, "Admin") ? "admin.png" :
               await _userManager.IsInRoleAsync(user, "Doctor") ? null : "user.png";
        }

UnitOfWork:

 public class UnitOfWork : IUnitOfWork, IDisposable
    {
        private readonly MedicardDbContext _context;

        public UnitOfWork(MedicardDbContext context)
        {
            _context = context;
        }

        private bool disposed = false;

        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        private void Dispose(bool disposing)
        {
            if (!this.disposed)
            {
                if (disposing)
                {
                    _context.Dispose();
                }
            }
            this.disposed = true;
        }

        public IGenericRepository<T> GenericRepository<T>() where T : class
        {
            IGenericRepository<T> repository = new GenericRepository<T>(_context);
            return repository;
        }

        public void Save()
        {
            _context.SaveChanges();
        }

        public async Task SaveAsync()
        {
            await _context.SaveChangesAsync();
        }
    }

The error is written somewhere along these lines:

return await _userManager.IsInRoleAsync(user, "Admin") ? "admin.png" :
                   await _userManager.IsInRoleAsync(user, "Doctor") ? null : "user.png";

and

var picture = await GetPictureForChat(targetUser);

and

var chatsViewModel = await _chatService.GetListChats(allUsers, currentUser);

But I don't know how to solve it.

What is your _userManager.IsInRoleAsync() is doing? Can you share _userManager.IsInRoleAsync() code? — Jr. Mediocre Coder, Feb 06 '23 at 20:37
@Jr.MediocreCoder UserManager is a class in Microsoft.AspNetcore.Identity — Andrij Matviiv, Feb 06 '23 at 20:47
You need to show the definition of your UnitOfWork class, as well as how you've defined your DI lifestyles. — David L, Feb 06 '23 at 21:03
@DavidL DI lifestyles, what exactly is here, the services or the unitofwork itself — Andrij Matviiv, Feb 06 '23 at 21:18
All of it potentially. This is usually caused by mismatched lifestyles that cause multiple threads to access the same context. How is Context and UnitOfWork registered, relative to your services? I am extremely suspicious of the fact that your unit of work holds the context and can then create repositories. — David L, Feb 06 '23 at 21:21
1) Reproduce the problem. 2) Reduce the code to the minimal amount that still reproduces the problem. — Stephen Cleary, Feb 07 '23 at 00:51
I'm not sure if the IOC cause this error, you can try to register dbcontext as Transient, Please refer to this [issue](https://stackoverflow.com/questions/48767910/entity-framework-core-a-second-operation-started-on-this-context-before-a-previ). — Xinran Shen, Feb 07 '23 at 07:11
@StephenCleary I don't understand the problem myself, I dropped everything that was there — Andrij Matviiv, Feb 07 '23 at 11:19
@XinranShen I'm a bit shocked, but the error disappeared by itself, is it normal? — Andrij Matviiv, Feb 07 '23 at 19:57
@StephenCleary I'm a bit shocked, but the error disappeared by itself, is it normal? — Andrij Matviiv, Feb 07 '23 at 19:57
@DavidL I'm a bit shocked, but the error disappeared by itself, is it normal? — Andrij Matviiv, Feb 07 '23 at 19:57
It most likely didn't disappear. You are just no longer hitting the cross-threading issue. — David L, Feb 07 '23 at 20:01

A second operation was started on this context instance before a previous operation completed

0 Answers0