Possible Object Cycle Detected

Question

I am trying to add a ProductGateway to a database and assign it a user. I am getting an A possible object cycle was detected . error but I am unsure how I can overcome this.

This is a 1:M relationship using Entity Framework Core. I am also in .NET 6.

The idea is that a user can exist in the database without any products but a product must be assigned a user.

var user = _repository.GetAll<UserGateway>().FirstOrDefault(u => u.Id == userId);

        if (user == null) throw new InvalidUserException();

        var productGateways = productDtos.Select(productDto => new ProductGateway
            {
                DateCreated = DateTime.Now,
                DateLastModified = DateTime.Now,
                Description = productDto.Description,
                Quantity = productDto.Quantity,
                Title = productDto.Title,
                Gsku = productDto.Sku,
                ImageUrl = "",
                UserId = userId
            })
            .ToList();

        user.Products = productGateways;
        foreach (var product in user.Products)
        {
            product.User = user;
        }

        _repository.AddRange(productGateways);
        _repository.Update(user);
        _repository.Commit();

        return productGateways;

Here is the properties on the UserGateway model

public string Auth0Id { get; set; }
public List<ProductGateway> Products { get; set; }

And the ProductGateway model

public string Title { get; set; }
public string Gsku { get; set; }
public string Description { get; set; }
public int Quantity { get; set; }
public string ImageUrl { get; set; }
public UserGateway User { get; set; }
public int UserId { get; set; }

I appreciate any help in advance! Cheers

EDIT: Here is my context class

public class Context : DbContext
{
    private readonly IConfiguration _configuration;
    private DbSet<ProductGateway> Products { get; set; }
    private DbSet<UserGateway> Users { get; set; }

    public Context(IConfiguration configuration)
    {
        _configuration = configuration;
    }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        var connectionString = _configuration.GetConnectionString("Context");
        optionsBuilder.UseSqlServer(connectionString);
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        foreach (var relationship in modelBuilder.Model.GetEntityTypes().SelectMany(e => e.GetForeignKeys()))
        {
            relationship.DeleteBehavior = DeleteBehavior.Restrict;
        }
    }
}

Answer 1

You have userId in productGateways, so it already has a reference to the user. Then you put one more reference to User In productGateway. After that, you put a list of productGateways to a user list. And here the cycle User -> ProductGateway -> user -> productGateway -> infinite.

Try to remove foreach and _repository.Update(user); calls, maybe it will help. Any way you should leave only one statement (add or update)