asp.net-mvc 使用 Automapper 更新现有实体 POCO
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Using Automapper to update an existing Entity POCO
提问by Paul Taylor
I am using EF4 DbContext to provide the model for an ASP.NET MVC app. I use ViewModels to provide data to the views and Automapper to perform the mapping between the EF POCOs and the ViewModels. Automapper does a great job but I'm not clear the best way to use it after the ViewModel is posted back to the controller to carry out an update.
我正在使用 EF4 DbContext 为 ASP.NET MVC 应用程序提供模型。我使用 ViewModel 向视图提供数据，并使用 Automapper 执行 EF POCO 和 ViewModel 之间的映射。Automapper 做得很好，但我不清楚在将 ViewModel 回发到控制器以执行更新后使用它的最佳方法。
My idea is to get POCO object using a key contained in the ViewModel. I then want to use Automapper to update the POCO with data from the ViewModel:
我的想法是使用 ViewModel 中包含的键来获取 POCO 对象。然后我想使用 Automapper 用 ViewModel 中的数据更新 POCO：
[HttpPost]
public ActionResult Edit(PatientView viewModel)
{
Patient patient = db.Patients.Find(viewModel.Id);
patient = Mapper.Map<ViewModel, Patient>(viewModel, patient);
...
db.SaveChanges();
return RedirectToAction("Index");
}
Two questions:
两个问题：
- The Find() method returns a Proxy rather than a POCO which causes Automapper to complain. How do I get the POCO instead of the Proxy?
- Is this best practice for performing an update?
- Find() 方法返回一个 Proxy 而不是 POCO，这会导致 Automapper 抱怨。我如何获得 POCO 而不是代理？
- 这是执行更新的最佳实践吗？
回答by Marius St?nescu
If you use Automapper like that, it returns a new Patient object and the references to the enity framework graph are not kept. You have to use it like this:
如果您像这样使用 Automapper，它会返回一个新的 Patient 对象，并且不会保留对实体框架图的引用。你必须像这样使用它：
[HttpPost]
public ActionResult Edit(PatientView viewModel)
{
Patient patient = db.Patients.Find(viewModel.Id);
Mapper.Map(viewModel, patient);
...
db.SaveChanges();
return RedirectToAction("Index");
}
回答by Paul Taylor
There seem to be two approaches to dealing with the EF proxy issue:
处理 EF 代理问题似乎有两种方法：
- Switch off
ObjectContext.ContextOptions.ProxyCreationEnabled, either for the whole application (in EF Context constructor or EDMX), or for the query where you need to guarantee getting an actual Entity object rather than a proxy. - Using an extension to Automapper, documented here: https://gist.github.com/935461.
- 关闭
ObjectContext.ContextOptions.ProxyCreationEnabled，对于整个应用程序（在 EF 上下文构造函数或 EDMX 中），或者对于需要保证获取实际实体对象而不是代理的查询。 - 使用 Automapper 的扩展，记录在此处：https: //gist.github.com/935461。
Note. The latter is commented with "Room for improvement. See: Automapper : mapping issue with inheritance and abstract base class on collections with Entity Framework 4 Proxy Pocos".
笔记。后者被评论为“改进空间。请参阅：Automapper：使用 Entity Framework 4 Proxy Pocos 的集合上的继承和抽象基类的映射问题”。
