NHibernate: Illegal attempt to associate a collection with two open sessions

Question

I'm having trouble with NHibernate, First let me say I'm not native English talker, OK, let get to point.

As i face this error, i searched over the internet, and saw lot of people talking about it, but most of them had issue with cascade attribute, and totally if i wanna say, non matched my case, or even if it did i couldn't get through.

My Database is so small, but a bit complex. My model files generated using Entity Developer.

As you can see there is inheritance, one-to-many and many-to-many relation ships,

As I am new to NHibernate, i write a test code, my normal test worked, till i add this many-to-many relation ship.

So i write this code:

//Owner o = new Owner
        //{
        //    //OwnerId = Guid.NewGuid(),
        //    CellPhone1 = null,
        //    CellPhone2 = "09132198895",
        //    Phone = "03114335502",
        //    Firstname = "Hassan",
        //    Lastname = "Faghihi",
        //    OwnerTitle = PersonTitle.Mr
        //};

        //OwnerFactory ownerFactory = new OwnerFactory();
        //ownerFactory.SaveOwner(o);

        //SellHouse sh = new SellHouse
        //{
        //    //ItemId = Guid.NewGuid(),
        //    Owner = o,
        //    Address = "dsasd",
        //    BuildYear = 1393,
        //    City = "Isfahan",
        //    Code = "A-512",
        //    Country = "Iran",
        //    Description = "Nothing",
        //    Dimensions = "4X5",
        //    Directions = Directions.North | Directions.South,
        //    Document = "dasd",
        //    Exchange = true,
        //    Facilities = Facilities.Elevator | Facilities.KichenMdfService | Facilities.Parking | Facilities.Warehouse,
        //    Floor = 4,
        //    HasYard = false,
        //    HouseType = HouseType.Apartment,
        //    IssueDate = DateTime.Now,
        //    Loan = 3124,
        //    Meter = 130,
        //    NumberOfBlocks = 4,
        //    NumberOfFloors = 0,
        //    OtherFacilities = "Nothing",
        //    Rooms = 2,
        //    ShareOfSixPart = 4.2f,
        //    State = "Isfahan",
        //    District = "kaveh",
        //    ExchangeDescription = "",
        //    Images = null,
        //    IsRented = false,
        //    Maps = null,
        //    MortgagePayed = 0,
        //    Price = 2222222,
        //    RentAmount = 0,
        //    Substructure = 4,
        //};

        GalleryFactory galleryFactory = new GalleryFactory();

        Gallery g = new Gallery
        {
            Image = Properties.Resources.jeans_texture03.ToByte()
        };

        galleryFactory.SaveGallery(g);

        SellHouseFactory sellHouseFactory = new SellHouseFactory();
        //factory.SaveSellHouse(sh);

        HashSet<Gallery> galleries = new HashSet<Gallery>();
        galleries.Add(g);

        SellHouse sellHouse = sellHouseFactory.GetSellHouses().FirstOrDefault();
        if (sellHouse != null)
        {
            comboBox1.SelectedIndex = (int)sellHouse.Owner.OwnerTitle;
            textBox1.Text = sellHouse.Owner.Firstname+sellHouse.Owner.Lastname;
            //sellHouse.Images = galleries;

            sellHouseFactory.SaveSellHouse(sellHouse);
        }

i create an object of Owner, then save it, and pass it to sellHouse, and set Images and Maps (which are my many-to-many relation) to null. so the sellHouse Created. then i was wonder how to add image or map to my sellHouse, So i pass a list containing one gallery element to sellHouse Maps property. And it generate "Illegal attempt to associate a collection with two open sessions", first i though the reason is because my Gallery didn't saved before i pass it to sell house, so i did as you can see on my code, and did it manually. But it still keep on generating that error...

I provide required file so, you can set up an example and understand my code better.

I'm very eager to hear your answer,cause my hands are tied do to my little knowledge over Hibernate and NHibernate.

Sources in DropBox:

enter link description here

Answer 1

Probably in all of your factory method you open a new session. But you have to open just one session in every thread (or transaction).