Fluent NHibernate自动映射在尝试提交列表时抛出“StaleStateException”<>

提交Order.OrderItems属性(IList)时,以下代码引发StaleStateException异常。例外情况全文如下:

NHibernate.dll中发生类型为“NHibernate.StaleStateException”的未处理异常

其他信息:意外的行计数:0;预期:1

我刚刚开始使用NHibernate,这对我来说毫无意义。有人能解释一下怎么回事吗?

如果我把这行注释掉 OrderItems=OrderItems

using System;
using System.Collections.Generic;
using System.IO;
using AutomappingSample.Domain;
using FluentNHibernate.AutoMap;
using FluentNHibernate.Cfg;
using FluentNHibernate.Cfg.Db;
using NHibernate;
using NHibernate.Cfg;
using NHibernate.Tool.hbm2ddl;

namespace AutomappingSample
{
    class Program
    {
        private const string DbFile = "AutomappingSample.db";
        private const bool useSqlServerCe = true;

        static void Main()
        {
            var factory = CreateSessionFactory();
            using (var session = factory.OpenSession())
            using(var tx = session.BeginTransaction())
            {
                var product1 = new Product
                                   {
                                       Name = "Apples",
                                       UnitPrice = 4.5m,
                                       Discontinued = true
                                   };
                var product2 = new Product
                                   {
                                       Name = "Pears",
                                       UnitPrice = 3.5m,
                                       Discontinued = false
                                   };
                session.Save(product1);
                session.Save(product2);

                var customer = new Customer
                                   {
                                       FirstName = "John",
                                       LastName = "Doe",
                                   };
                session.Save(customer);

                var orderItems = new List<OrderItem>
                                     {
                                         new OrderItem {Id = 1, Quantity = 100, Product = product1},
                                         new OrderItem {Id = 2, Quantity = 200, Product = product2},
                                     };
                var order = new Order()
                                {
                                    Customer = customer, 
                                    Id = 1, 
                                    OrderDate = DateTime.Now, 

                                    // CAUSES FOLLOWING EXCEPTION WHEN COMMIT:
                                    //      An unhandled exception of type 'NHibernate.StaleStateException' 
                                    //      occurred in NHibernate.dll
                                    //
                                    //      Additional information: Unexpected row count: 0; expected: 1
                                    OrderItems = orderItems
                                };
                session.Save(order);

                // EXCEPTION IS THROWN HERE
                tx.Commit();

          }

            Console.WriteLine("Hit enter to exit...");
            Console.ReadLine();
        }

        private static ISessionFactory CreateSessionFactory()
        {
            IPersistenceConfigurer persistenceConfigurer;
            if (useSqlServerCe)
                persistenceConfigurer =
                    MsSqlCeConfiguration.Standard.ConnectionString(c => c.Is("Data Source=AutomappingSample.sdf"));
            else
                persistenceConfigurer = SQLiteConfiguration.Standard.UsingFile(DbFile);

            return Fluently.Configure()
                .Database(persistenceConfigurer)
                .Mappings(m => m.AutoMappings.Add(
                                   AutoPersistenceModel
                                       .MapEntitiesFromAssemblyOf<Customer>()
                                       .WithSetup(s => { s.IsBaseType = type => type == typeof (EntityBase); })
                                       .Where(t => t.Namespace.EndsWith("Domain"))
                                       .ConventionDiscovery.Add<MyStringLengthConvention>()
                                       .ConventionDiscovery.Add<MyIdConvention>()
                                       .ConventionDiscovery.Add<MyForeignKeyConvention>()
                                   ))
                .ExposeConfiguration(BuildSchema)
                .BuildSessionFactory();
        }

        private static void BuildSchema(Configuration config)
        {
            // delete the existing db on each run (only for SQLite)
            if (File.Exists(DbFile))
                File.Delete(DbFile);

            // this NHibernate tool takes a configuration (with mapping info in)
            // and exports a database schema from it
            new SchemaExport(config)
                .Create(true, true);
        }
    }
}

namespace AutomappingSample.Domain
{
    public class EntityBase
    {
        public virtual int Id { get; set; }
    }
}

using System;
using System.Collections.Generic;

namespace AutomappingSample.Domain
{
    public class Order : EntityBase
    {
        public virtual DateTime OrderDate { get; set; }
        public virtual Customer Customer { get; set; }
        public virtual IList<OrderItem> OrderItems { get; set; }
    }
}

namespace AutomappingSample.Domain
{
    public class OrderItem : EntityBase
    {
        public virtual int Quantity { get; set; }
        public virtual Product Product { get; set; }
    }
}