保存更改时，EF 4.3 CF不会更新关系 [英] EF 4.3 CF does not update relationships when saving changes

问题描述

我有一个ClubItem对象与关系集ICollection ClubUsers。我从上下文加载了一个ClubItem，并向CluItem添加了几个新用户。将ClubItem保存在断开状态时，上下文不会将新的ClubUsers看作新的实体。如何告诉上下文有什么变化？我已经用这个来改变ClubItem的实体状态：

  public virtual void Update（IEntity entityToUpdate）
 {
 DbSet.Attach（entityToUpdate）; 
 Context.Entry（entityToUpdate）.State = EntityState.Modified; 
 
 SaveChanges（）; 
} 
  

解决方案

在具体情况下，您可以可能只是删除附加行。 附加将包含其他分离实体的分离实体放在对象图形中，进入状态不变。当您将状态更改为修改时，它仅影响父实体，孩子仍然处于状态不变。如果您调用 SaveChanges ，则不会保存子项，因为它们的状态为不变。

如果您不调用附加，孩子们保持分离，直到 SaveChanges 被调用在哪里EF将假定它们是新实体（因为它们不附加到上下文），并将其状态设置为添加。然后他们将被插入数据库。

但是，如果删除 Attach 行，则无法使用该方法更新现有的父母和现有孩子之间的关系。

通常，当分离的实体包含已更改的实体的子集合时，添加了实体已被删除的位置从您通常必须从数据库重新加载原始对象图并将更改合并到其中。复杂分离对象图的这种更新不以通用方式工作，并且将需要实体类型特定的代码。例如： https://stackoverflow.com/a/5540956/270591

I've got a ClubItem object with a relationship collection ICollection ClubUsers. I load a ClubItem from the context and add a couple of new users to the CluItem. When saving the ClubItem in a disconnected state the context does not see the new ClubUsers as new entities. How to tell the context that something changed? I allready use this to change entitystate of the ClubItem:

    public virtual void Update(IEntity entityToUpdate)
    {
        DbSet.Attach(entityToUpdate);
        Context.Entry(entityToUpdate).State = EntityState.Modified;

        SaveChanges();
    } 

解决方案

In your specific case you can probably just remove the Attach line. Attach puts the detached entity including other detached entities in the object graph into state Unchanged. When you change the state to Modified it affects only the parent entity, the children are still in state Unchanged. If you call SaveChanges the children won't be saved because their state is Unchanged.

If you don't call Attach the children stay detached until SaveChanges is called where EF will assume that they are new entities (because they are not attached to the context) and set their state to Added. Then they will be inserted into the database.

However, if you remove the Attach line you cannot use the method anymore to update the relationship between existing parent and existing children.

Generally, when the detached entity contains a child collection of entities that are changed, added of where entities have been removed from you normally have to reload the original object graph from the database and merge the changes into it. Such an Update of a complex detached object graph does not work in a generic way and will require entity type specific code. An example is here: https://stackoverflow.com/a/5540956/270591

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