Question

我有以下C＃类（简化）：

class Entity {
    Guid Id { get; set;}
    ISet<Uri> Urls { get; set; }
}

我想将它映射到下面的表结构：

TABLE Entity (
   Id uniqueidentifier PRIMARY KEY       
)

TABLE EntityUrls (
   Id uniqueidentifier PRIMARY KEY,
   EntityId uniqueidentifier FOREIGN KEY REFERENCES(Entity.Id),
   Uri varchar(250)
)

我几乎可以使用<set>来映射它

<set name="Urls" table="EntityUrls">
  <key column="EntityId"/>
  <element column="Uri" type="..."/>
</set>

但是如何映射EntityUrls.Id列（至少在INSERT上生成Guid）？或者通常建议在这种情况下使用复合PK？

Answer 1

您可以尝试创建实现ICompositeUserType的自定义用户类型：

<set name="Urls" table="EntityUrls">
  <key column="EntityId"/>

  <element type="UserTypes.UriCompositeUserType">
    <column name="Id" />
    <column name="Uri" />
  </element>
</set>

以下是NHibernate对ICompositeUserType所说的内容：

A UserType that may be dereferenced in a query. This interface allows a custom type to define "properties". These need not necessarily correspond to physical .NET style properties. A ICompositeUserType may be used in almost every way that a component may be used. It may even contain many-to-one associations. Implementors must be immutable and must declare a public default constructor. Unlike UserType, cacheability does not depend upon serializability. Instead, Assemble() and Disassemble() provide conversion to/from a cacheable representation.

将<set> + <element>映射到NHibernate </element> </set>中具有代理项id的表

1 个答案: