在LINQ实体连接问题 [英] Entity attachment issues in LINQ

问题描述

我想我从一个表单POST接收后，到LINQ实体连接到数据上下文。但是，我得到的是以下异常：

I am trying to attach a LINQ entity to the data context after I receive it from a form POST. However, all I get is the following exception:

An entity can only be attached as modified without original state if it declares a version member or does not have an update check policy.

我也尝试安装原始行，像这样：

I have also tried attaching the original row, like so:

dataContext.People.Attach(person, originalPerson);

在这种情况下，我得到了以下异常：

In this case, I get the following exception:

Object reference not set to an instance of an object.

下面是我在控制器中的code：

Here's the code in my controller:

[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Edit(int id, Person person) {
    var prevPerson = dataContext.People.Single(p => p.ID == id);
    dataContext.People.Attach(person, prevPerson);
    dataContext.SubmitChanges();
    return Redirect("~/People/Index");
}

这是我做错了什么在这里的任何想法？如果需要的话我可以张贴实体code。

Any ideas on what I'm doing wrong here? I can post the entity code if needed.

推荐答案

在LinqToSQL设计器中设置的所有检查更新为从不，当你连接调用它像这样：

In the LinqToSQL designer set all of the Update Checks to Never and when you attach call it like so:

 context.entity.Attach(entity, true);

另外，你也可以抓住从数据库实体，并使用从发布的实体中的数据进行更改，然后提交，作为一个改变。

Alternatively, you could also grab the entity from the db and change it using the data from the POSTed entity, then submit that as a change.

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