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POEF4.1 : How to deal with items being added to an Object's collection
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  1. POEF4.1 : How to deal with items being added to an Object's collection
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    copied!<p>I'm using EF4.1 for the first time (so be patient with me) but I just cant get to grips with how I can add new items to a sub collection of an object and then save the object.</p> <p>For example, with the classes below, I can initially save the TravelTicket (containing multiple People) into my database, but as soon as I add a new person and then try to save the TravelTicket again I get:</p> <p>An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key.</p> <p>Can anyone help?</p> <pre><code>public class TravelTicket { public int Id { get; set; } public string Destination { get; set; } public virtual List&lt;Person&gt; Members { get; set; } } public class Person { public int Id { get; set; } public string Name{ get; set; } } </code></pre> <p><strong>EDITED: All relevant code added as requested:</strong></p> <p>Domain Models:</p> <pre><code>public class TravelTicket { public int Id { get; set; } public string Destination { get; set; } public virtual ICollection&lt;Person&gt; Members { get; set; } } public class Person { public int Id { get; set; } public string Name { get; set; } } </code></pre> <p>The DB Context:</p> <pre><code>public class TicketContext : DbContext { public TicketContext() : base("TicketStore") { } public DbSet&lt;TravelTicket&gt; TravelTickets { get; set; } public DbSet&lt;Person&gt; People { get; set; } } </code></pre> <p>The Repository (relevant methods only):</p> <pre><code>public class TicketRepository : ITicketRepository { TicketContext context = new TicketContext(); public void InsertOrUpdate(TravelTicket quoteContainer) { if (quoteContainer.Id == default(int)) { // New entity context.TravelTickets.Add(quoteContainer); } else { // Existing entity context.Entry(quoteContainer).State = EntityState.Modified; } } public void Save() { try { context.SaveChanges(); } catch (DbEntityValidationException dbEx) { foreach (var validationErrors in dbEx.EntityValidationErrors) { foreach (var validationError in validationErrors.ValidationErrors) { Trace.TraceInformation("Property: {0} Error: {1}", validationError.PropertyName, validationError.ErrorMessage); } } } } } public interface ITicketRepository { void InsertOrUpdate(TravelTicket travelTicket); void Save(); } </code></pre> <p>The consuming (example) MVC Controller code:</p> <pre><code>public class TicketSaleController : Controller { private readonly ITicketRepository ticketRepository; public TicketSaleController() : this(new TicketRepository()) { } public TicketSaleController(ITicketRepository ticketRepository) { this.ticketRepository = ticketRepository; } public ActionResult Index() { TravelTicket ticket = new TravelTicket(); ticket.Destination = "USA"; List&lt;Person&gt; travellers = new List&lt;Person&gt;(); travellers.Add(new Person { Name = "Tom" }); travellers.Add(new Person { Name = "Dick" }); travellers.Add(new Person { Name = "Harry" }); ticket.Members = travellers; ticketRepository.InsertOrUpdate(ticket); ticketRepository.Save(); Session["Ticket"] = ticket; return RedirectToAction("Next"); } public ActionResult Next() { TravelTicket ticket = (TravelTicket)Session["Ticket"]; ticket.Members.Add(new Person { Name = "Peter" }); ticket.Members.Add(new Person { Name = "Paul" }); ticketRepository.InsertOrUpdate(ticket); ticketRepository.Save(); return View(); } } </code></pre> <p>The call "ticketRepository.InsertOrUpdate(ticket);" on the "Next" method causes the exception:</p> <p><strong>An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key.</strong></p> <p>FURTHER EDIT: If I pull the object back from the database after its been saved instead of pulling the object from the session, adding the 2 new persons works OK:</p> <p>Works: TravelTicket ticket = ticketRepository.Find(ticketId); ticket.Members.Add(new Person { Name = "Peter" }); ticket.Members.Add(new Person { Name = "Paul" }); ticketRepository.InsertOrUpdate(ticket); ticketRepository.Save();</p> <p>Doesn't Work: TravelTicket ticket = (TravelTicket)Session["Ticket"]; ticket.Members.Add(new Person { Name = "Peter" }); ticket.Members.Add(new Person { Name = "Paul" }); ticketRepository.InsertOrUpdate(ticket); ticketRepository.Save();</p>
 

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