Question

我正在尝试在此处执行教程：http://www.asp.net/entity-framework/tutorials/handling-concurrency-with-the-entity-framework-in-an-asp-net-mvc-application

在ActionResult Edit中，我有以下代码：

public ActionResult Edit(Product product)
{
    try
    {
        if (ModelState.IsValid)
        {
            db.Entry(product).State = EntityState.Modified;
            db.SaveChanges();
            return RedirectToAction("Index");
        }
    }
    catch(DbUpdateConcurrencyException ex)
    {

                        var entry = ex.Entries.Single();
        var databaseValuesObj = entry.GetDatabaseValues().ToObject();
        var databaseValues = (Product)databaseValuesObj;
        var clientValues = (Product)entry.Entity;
        if (databaseValues.Name != clientValues.Name)
            ModelState.AddModelError("Name", "Current value: "
                + databaseValues.Name);
        if (databaseValues.Description != clientValues.Description)
            ModelState.AddModelError("Description", "Current value: "
                + String.Format("{0:c}", databaseValues.Description));
        if (databaseValues.ControllingStudentId != clientValues.ControllingStudentId)
            ModelState.AddModelError("ControllingStudentId", "Current value: "
                + String.Format("{0:d}", databaseValues.ControllingStudentId));
        ModelState.AddModelError(string.Empty, "The record you attempted to edit "
            + "was modified by another user after you got the original value. The "
            + "edit operation was canceled and the current values in the database "
            + "have been displayed. If you still want to edit this record, click "
            + "the Save button again. Otherwise click the Back to List hyperlink.");
        product.Timestamp = databaseValues.Timestamp;
    }
    catch (DataException)
    {
        //Log the error (add a variable name after Exception)
        ModelState.AddModelError(string.Empty, "Unable to save changes. Try again, and if the problem persists contact your system administrator.");
    }

    return View(product);
}

在var databaseValuesObj = entry.GetDatabaseValues().ToObject();行，我得到一个像这样的例外：

System.Data.EntitySqlException was unhandled by user code
  Message=Type 'MvcApplication3.DAL.Product' could not be found. Make sure that the required schemas are loaded and that the namespaces are imported correctly. Near type name, line 1, column 119.
  Source=System.Data.Entity
  Column=119
  ErrorContext=type name, line 1, column 119
  ErrorDescription=Type 'MvcApplication3.DAL.Product' could not be found. Make sure that the required schemas are loaded and that the namespaces are imported correctly.
  Line=1
 ...

我的问题是，如何在Product类的哪个位置显示它？它在项目中，我在顶部有使用声明。为什么不能找到它？

编辑：根据以下回复，我将代码更改为：

        var entry = ex.Entries.Single();
        var currentValues = entry.CurrentValues.Clone();
        entry.Reload();
        entry.CurrentValues.SetValues(currentValues);
        var clientValues = (Product)entry.Entity;
        var databaseValues = (Product)entry.OriginalValues.ToObject();

这似乎解决了这个问题。但我认为如果删除该行会有问题。我目前的问题不会出现这个问题，所以对我来说这是一个很好的解决方案。谢谢！

Answer 1

当上下文位于不同的项目中时，这是一个已知问题。除了将上下文移动到同一个项目之外，目前还没有解决方法。

http://social.msdn.microsoft.com/Forums/en-HK/adodotnetentityframework/thread/fa67aa0e-3bca-44a5-9e00-af6362a539a7

修改的实际上我把它拿回来 - 自从我上次读这篇文章以来，现在有一个解决方法。很酷：）

尝试访问DbUpdateConcurrencyException的GetDatabaseValues（）实体时出现EntitySqlException

1 个答案: