Question

我有三个EntityFramework（4.3）对象，一个Member，Address和一个State。它们看起来像这样：

public class Member
{
    public int Id { get; set; }
    public virtual Address Address { get; set; }
    /*other properties removed for brevity*/
}

public class Address
{
    public int Id { get; set; }
    public virtual State State { get; set; }
    /*other properties removed for brevity*/
}

public class State
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Abbreviation { get; set; }
    public virtual ICollection<Address> Address { get; set; }
}

当我更新地址关系时，一切正常。请参阅以下代码：

[HttpPost]
public ActionResult Update(MemberUpdateModel model)
{
    if (!ModelState.IsValid)
    {
        model.SetStateSelectList(_db, model.SelectedStateId);
        return View(model);
    }

    _db.Entry(model.Member).State = EntityState.Modified;
    _db.Entry(model.Member.Address).State = EntityState.Modified;

    _db.SaveChanges(); // works

    return RedirectToAction("Index");
}

然后我添加地址/状态关系的更新，如下所示：

[HttpPost]
public ActionResult Update(MemberUpdateModel model)
{
    if (!ModelState.IsValid)
    {
        model.SetStateSelectList(_db, model.SelectedStateId);
        return View(model);
    }

    _db.Entry(model.Member).State = EntityState.Modified;
    _db.Entry(model.Member.Address).State = EntityState.Modified;

    // added for address/state relationship
    var selectedState = _db.States.FirstOrDefault(q => q.Id == model.SelectedStateId);
    model.Member.Address.State = selectedState;

    _db.SaveChanges();

    return RedirectToAction("Index");
}

当我们运行上面的代码时，我们收到以下错误：

Store update, insert, or delete statement affected an unexpected number of rows (0). Entities may have been modified or deleted since entities were loaded. Refresh ObjectStateManager entries.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.Data.OptimisticConcurrencyException: Store update, insert, or delete statement affected an unexpected number of rows (0). Entities may have been modified or deleted since entities were loaded. Refresh ObjectStateManager entries.

我做错了什么导致这种行为？

Answer 1

“OptimisticConcurrencyException”看起来像是一个有意义的线索。 This discussion可能有用。

Answer 2

我们更改了更新操作以首先查询现有数据，然后使用发布的数据更新对象。

[HttpPost]
public ActionResult Update(MemberUpdateModel model)
{
    if (!ModelState.IsValid)
    {
        model.SetStateSelectList(_db, model.SelectedStateId);
        return View(model);
    }

    var newModel = new MemberUpdateModel();
    newModel.Member = _db.Members.Include("Address").FirstOrDefault(q => q.Id == model.Member.Id);
    newModel.Member.Address.State = _db.States.FirstOrDefault(q => q.Id == model.SelectedStateId);

    bool success = TryUpdateModel(newModel);
    if (success)
    {
        _db.SaveChanges();
    }
    else
    {
        throw new Exception("TryUpdateModel() Failed");
    }

    return RedirectToAction("Index");
}

这很有效。

编辑与EntityFramework的关系时，为什么会出现错误？

2 个答案: