c# - EF4.1 : How to deal with items being added to an Object's collection

Question

我是第一次使用 EF4.1(请耐心等待)，但我无法掌握如何将新项目添加到对象的子集合，然后保存该对象。

例如，对于下面的类，我最初可以将 TravelTicket(包含多个人)保存到我的数据库中，但是当我添加一个新人然后再次尝试保存 TravelTicket 时，我得到:

ObjectStateManager 中已存在具有相同键的对象。 ObjectStateManager 无法跟踪具有相同键的多个对象。

有人能帮忙吗？

public class TravelTicket
{
  public int Id { get; set; }
  public string Destination { get; set; }
  public virtual List<Person> Members { get; set; }
}

public class Person
{
  public int Id { get; set; }
  public string Name{ get; set; }
}

编辑:所有相关代码按要求添加:

领域模型:

public class TravelTicket
{
    public int Id { get; set; }
    public string Destination { get; set; }
    public virtual ICollection<Person> Members { get; set; }
}

public class Person
{
    public int Id { get; set; }
    public string Name { get; set; }
}

数据库上下文:

public class TicketContext : DbContext
{
    public TicketContext()
        : base("TicketStore")
    { }

    public DbSet<TravelTicket> TravelTickets { get; set; }
    public DbSet<Person> People { get; set; }
}

存储库(仅相关方法):

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();
}

消费(示例)MVC Controller 代码:

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<Person> travellers = new List<Person>();
        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();
    }
}

调用“ticketRepository.InsertOrUpdate(ticket);”在“Next”方法上导致异常:

ObjectStateManager 中已存在具有相同键的对象。 ObjectStateManager 无法跟踪具有相同键的多个对象。

进一步编辑:如果我在保存对象后从数据库中拉回对象而不是从 session 中拉取对象，则添加 2 个新人可以正常工作:

作品: TravelTicket ticket = ticketRepository.Find(ticketId); ticket.Members.Add(new Person { Name = "Peter"}); ticket.Members.Add(new Person { Name = "Paul"}); ticketRepository.InsertOrUpdate(ticket); ticketRepository.Save();

不起作用: TravelTicket ticket = (TravelTicket)Session["Ticket"]; ticket.Members.Add(new Person { Name = "Peter"}); ticket.Members.Add(new Person { Name = "Paul"}); ticketRepository.InsertOrUpdate(ticket); ticketRepository.Save();

Answer 1

我需要查看您用来添加项目的代码，然后保存它们。直到那几个通用的建议。

看起来您正在使用长期存在的上下文来做您的事情。使用短暂的生活环境是一个很好的做法，就像这样:

• 实例上下文
• 做一个单一的操作
• 处理上下文

冲洗并重复您必须执行的每项操作。在遵循这一良好做法的同时，您可能会间接解决您的问题。

同样，如需更具体的帮助，请发布您正在使用的代码；)