如何创建NHibernate的HasManyToMany关系 [英] How to create NHibernate HasManyToMany relation
问题描述
我知道大约有HasManyToMany问题，但这次我想把几个字段到像'说明，CreationDate'中间表。
I know there are questions about HasManyToMany but this time I want to put couple fields into middle table like 'Description, CreationDate'.
有关我的情况，我不想绑定双向。我有公司，个人和地址表。
而且每个公司或个人可能有超过1个地址。
在这种情况下我该怎么办？
我应该怎么写的类和映射的code？
For my situation I don't want to bind two way. I have company, person and address tables. And every company or person may have more than 1 address. In this situation what should I do? How should I write the code of classes and mappings?
下面你可以看到表：
推荐答案
在这种情况下，答案是pretty简单。不要使用许多一对多。使用配对对象。究竟对你提到的原因：扩展的配对对象，具有多个属性：
In this case the answer is pretty simple. Do not use many-to-many. Use pairing object. Exactly for the reasons you've mentioned: Extend the pairing object with more properties:
这里检查 24。最佳实践的，一个引用：
Check here 24. Best Practices, a cite:
良好的用例是罕见的。大多数时候，你需要存储在链接表的更多信息。在这种情况下，它是最好使用两个一一对多关联到一个中间链路类。事实上，我们认为大多数协会是一个一对多和多对一的，你应该使用其他任何关联的风格的时候要小心，问问自己，是否真的neccessary。
Don't use exotic association mappings.
Good usecases for a real many-to-many associations are rare. Most of the time you need additional information stored in the "link table". In this case, it is much better to use two one-to-many associations to an intermediate link class. In fact, we think that most associations are one-to-many and many-to-one, you should be careful when using any other association style and ask yourself if it is really neccessary.
换句话说，创建一到不少来自boht结束，关系闯民宅的配对对象多到一从配对对象。
Other words, create the one-to-many relations refering the pairing objects from boht ends, and many-to-one from the pairing object.
也检查这些：
- Hibernate: many-to-many relationship table as entity
- NHibernate Bidirectional Many-to-Many Mapping List / Bag
- Nhibernate: How to represent Many-To-Many relationships with One-to-Many relationships?
地址和公司的一个例子。首先配对对象
An example of the Address and Company. First Pairing object
public class AddressCompany
{
// the relation to both sides
public virtual Address Address { get; set; }
public virtual Company Company { get; set; }
// many other settings we need
public virtual string Description { get; set; }
public virtual DateTime CreationDate { get; set; }
...
}
在坚果壳的地址和公司名称：
the Address and Company in a nut-shell:
public class Address
{
public virtual IList<AddressCompany> Companies { get; set; }
...
}
public class Company
{
public virtual IList<AddressCompany> Addresses { get; set; }
...
}
如预期的映射：
public AddressMap()
{
HasMany(x => x.Companies)
...
}
public CompanyMap()
{
HasMany(x => x.Addresses)
...
}
public AddressCompanyMap()
{
References(x => x.Address)..
References(x => x.Company)..
...
}
所以，这是重新presenting的配对对象
So, this is representing the Pairing object
好了，但现在我们可以找到一些公司日期之后创建的：
Well, but now we can find some Companies Created after a date:
var subquery = QueryOver.Of<AddressCompany>()
.Where(c => c.CreationDate > new DateTime(2000, 1, 1))
.Select(c => c.Company.ID);
var query = session.QueryOver<Company>()
.WithSubquery
.WhereProperty(c => c.ID)
.In(subquery)
...;
这样我们也可以在地址过滤公司...
This way we can also filter Company over the Address...
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