NHibernate多对多在插入前删除所有关联 [英] NHibernate Many-To-Many Is Deleting All Associations Before Inserting

问题描述

我有一个 Users 表和一个 Networks 表，它们之间存在多对多关系(一个用户可能长到多个网络，一个网络可能包含多个用户).多对多关系保存在只有两列 UserId 和 NetworkId 的UserNetworks"表中.

I have a Users table and a Networks table with a many-to-many relationship between them (a user may be long to multiple networks and a network may contain many users). The many-to-many relationship is held in a "UserNetworks" table that simply has two columns, UserId and NetworkId.

我的课程是这样的:

public class User
{
    public IList<Network> Networks {get; set;}
}

public class Network
{
    public IList<Usre> Users {get; set;}
}

这些多对多集合的 NHibernate 映射如下所示:

The NHibernate mappings for these many-to-many collections looks like this:

用户.hbm.xml:

User.hbm.xml:

<bag name="Networks" table="UserNetworks" cascade="save-update" inverse="true">
    <key column="UserId" />
    <many-to-many class="Network" column="NetworkId" />
</bag>

Network.hbm.xml:

Network.hbm.xml:

<bag name="Users" table="UserNetworks" cascade="save-update">
    <key column="NetworkId" />
    <many-to-many class="User" column="UserId" />
</bag>

在我的代码中，我在用户和网络之间创建了一个关联，如下所示:

In my code, I create an association between a user and a network like so:

user.Networks.Add(network);
network.Users.Add(user);

我希望 SQL 运行只对 UserNetworks 表执行一次 INSERT.相反，它对 NetworkID = X 的 UserNetworks 表执行 DELETE，然后继续将所有 UserNetworks 行连同新关联一起重新插入.

I would expect the SQL run to simply perform one INSERT to the UserNetworks table. Instead, it executes a DELETE on the UserNetworks table with NetworkID = X, then proceeds to reinsert all the UserNetworks rows back in along with the new association.

我做错了什么?

推荐答案

行为是设计使然.看，NH 不知道列表中的当前/新/已删除内容.因此，删除所有内容并在列表中插入任何内容都是有意义的.

The behaviour is by design. See, NH do not know what's current/new/deleted in the list. So by deleting all and inserting whatever in the list will make sense.

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