如何处理更新实体.NHibernate+ASP.NET MVC

我无法更新以前创建的实体。我收到一个StaleObjectException异常，消息为：

Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect): [Project.DomainLayer.Entities.Employee#00000000-0000-0000-0000-000000000000]

我不与任何人共享更新过程。怎么了？

数据访问/DI

public class DataAccessModule : Ninject.Modules.NinjectModule
{
    public override void Load()
    {
        this.Bind<ISessionFactory>()
            .ToMethod(c => new Configuration().Configure().BuildSessionFactory())
            .InSingletonScope();
        this.Bind<ISession>()
            .ToMethod(ctx => ctx.Kernel.TryGet<ISessionFactory>().OpenSession())
            .InRequestScope();
        this.Bind(typeof(IRepository<>)).To(typeof(Repository<>))
            .InRequestScope();
    }
}

数据访问/映射

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="Project.DomainLayer"   namespace="Project.DomainLayer.Entities">
<class name="Employee" optimistic-lock="version">
    <id name="ID" column="EmployeeID" unsaved-value="00000000-0000-0000-0000-000000000000">
        <generator class="guid.comb" />
    </id>
    <version name="Version" type="Int32" column="Version" />
    <!-- properties -->
    <property name="EmployeeNumber" />
    <!-- ... -->
    <property name="PassportRegistredOn" not-null="true" />
    <!-- sets -->
    <set name="AttachedInformation" cascade="all">
        <key column="EmployeeID" />
        <element column="Attachment" />
    </set>
    <set name="TravelVouchers" cascade="all">
        <key column="EmployeeID" />
        <one-to-many class="TravelVoucher" />
    </set>
  </class>
</hibernate-mapping>

数据访问/存储库

public class Repository<T> : IRepository<T> where T : AbstractEntity<T>, IAggregateRoot
{
    private ISession session;
    public Repository(ISession session)
    {
        this.session = session;
    }
    // other methods are omitted
    public void Update(T entity)
    {            
        using(var transaction = this.session.BeginTransaction())
        {
            this.session.Update(entity);
            transaction.Commit();
        }
    }
    public void Update(Guid id)
    {            
        using(var transaction = this.session.BeginTransaction())
        {
            this.session.Update(this.session.Load<T>(id));
            transaction.Commit();
        }
    }
} 

控制器内部

public class EmployeeController : Controller
{
    private IRepository<Employee> repository;
    public EmployeeController(IRepository<Employee> repository)
    {
        this.repository = repository;
    }        
    public ActionResult Edit(Guid id)
    {
        var e = repository.Load(id);
        return View(e);
    }
    [AcceptVerbs(HttpVerbs.Post)]
    public ActionResult Edit(Employee employee)
    {
        if(ModelState.IsValid)
        {
            repository.Update(employee);
            return RedirectToAction("Deatils", "Employee", new { id = employee.ID });
        }
        else
        {
            return View(employee);
        }
    }
}

如何更新我的实体？谢谢

编辑

所以我在标记中添加了unsaved-value="{Guid.Empty goes here}"。此外，我还试着做下一件事：

public void Update(T entity)
{
    using(var transaction = this.session.BeginTransaction())
    {
        try
        {
            this.session.Update(entity);
            transaction.Commit();
        }
        catch(StaleObjectStateException ex)
        {
            try
            {
                session.Merge(entity);
                transaction.Commit();
            }
            catch
            {
                transaction.Rollback();
                throw;
            }
        }
    }
}

这给了我同样的效果。。在Merge之后的transaction.Commit();给出了相同的例外。

此外，我想知道是否应该使用隐藏输入在Edit视图上公开实体ID？

编辑

所以实体真的分离了。当它传递到控制器时，ID等于Guid.Empty。我该如何处理Merge还是Reattach？