Question

我有一个ASP.NET MVC POST操作，用于在提交表单时保存实体。它适用于插入但不适用于更新，数据库不会被调用，因此它显然没有跟踪更改，因为它是“分离的”。我正在使用带有.NET 4的实体框架：

//POST: /Developers/Save/
        [AcceptVerbs(HttpVerbs.Post)]
        public ActionResult Save(Developer developer)
        {
            developer.UpdateDate = DateTime.Now;
            if (developer.DeveloperID == 0)
            {//inserting new developer.
                DataContext.DeveloperData.Insert(developer);
            }
            //save changes - TODO: doesn't update...
            DataContext.SaveChanges();
            //redirect to developer list.
            return RedirectToAction("Index");
        }

非常感谢任何想法，谢谢，

贾斯汀

Answer 1

您永远不会将新数据应用于上下文。您可以使用Stub Entity技巧来避免查询。

尝试类似这样的事情（如果有错误，请从内存，sry）：

public ActionResult Save(Developer developer)
{
     developer.UpdateDate = DateTime.Now;

     Developer d = new Developer { ID = developer.ID };
     DataContext.Attach(d);

     DataContext.ApplyCurrentValues(developer);
     DataContext.SaveChanges();
}

Answer 2

很抱歉发布到较旧的帖子但我遇到了这个问题，我发现的解决方案比我相信的效率更高一些。问题是当您将实体附加回上下文时，实体EntityState将重置为“Unchanged”。所以你必须把它恢复到“修改”状态。最简单的方法是将属性设置为自身。

//POST: /Developers/Save/
    [AcceptVerbs(HttpVerbs.Post)]
    public ActionResult Save(Developer developer)
    {
        developer.UpdateDate = DateTime.Now;
        if (developer.DeveloperID == 0)
        {//inserting new developer.
            DataContext.DeveloperData.Insert(developer);
        }else{
            DataContext.Attach(developer);
        }

        **developer.DeveloperID = developer.DeveloperID;
          // Just ran into a problem that using the primary key like this doesn't reset the EntityState... but using string fields does change it so take that into consideration.

          // OR IN YOUR CASE YOU CAN JUST MOVE DOWN THE UpdateDate set statement above like:

        developer.UpdateDate = DateTime.Now;**

        //save changes
        DataContext.SaveChanges();
        //redirect to developer list.
        return RedirectToAction("Index");
    }

这些更改中的任何一个都应该解决更新问题。

我仍在寻找的原因是这对我来说似乎是一种黑客攻击，并且必须采用“更清洁”的方式来实现它。我仍然觉得这是所提供解决方案中最便宜的。我有点震惊，设置一个属性自己触发了属性更改事件。我假设它会检查以确保值不相同。

Answer 3

有关更新已分离对象的信息，请参阅here，但以下内容可以帮助您（作为if(developer.DeveloperID == 0)的else块）：

else
{
    var original = DataContext.DeveloperData
                              .Where(d => d.DeveloperID == developer.DeveloperID)
                              .FirstOrDefault();

    DataContext.DeveloperData.Attach(developer);
    context.ApplyOriginalValues(original);   
}

Answer 4

如果断开连接，则必须重新连接：

MSDN: Attaching and Detaching Objects (Entity Framework)

你可能想要：

    [AcceptVerbs(HttpVerbs.Post)]
    public ActionResult Save(Developer developer)
    {
        developer.UpdateDate = DateTime.Now;
        if (developer.DeveloperID == 0)
        {//inserting new developer.
            DataContext.Attach(developer);
        }
        //save changes - TODO: doesn't update...
        DataContext.SaveChanges();
        //redirect to developer list.
        return RedirectToAction("Index");
    }

ASP.NET MVC＆amp;独立实体不会保存

4 个答案: