NHibernate的陷井

      这几天公司准备用NHibernate作为基础框架，上网搜了搜，NHibernate官网提供了几个版本，最基础的是NHibernate，然后NHibernate.Burrow是对前者做了一些封装，NHibernate.Burrow.AppBlock则进一步进行了封装，看了下，确实很方便，于是自己动手写点玩意。

      帮助文档都是E文版，所有又好用又不要钱的玩意好像都是外国人搞出来的，好在还不难懂。官网下了个例子，结果中了一个招。请看帮助文档：

 

Now consider a model of the relationships between Customer, Order and LineItem and Product. There is a one-to-many association between Customer and Order, but how should we represent Order / LineItem / Product? I've chosen to map LineItem as an association class representing the many-to-many association between Order and Product. In NHibernate, this is called a composite element.

Code
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
    assembly="" namespace="">

    <class name="Customer" table="customers">
        <id name="Id" column="id">
            <generator class="native"/>
        </id>
        <property name="Name" column="name"/>
        <set name="Orders" inverse="true" lazy="true">
            <key column="customer_id"/>
            <one-to-many class="Order"/>
        </set>
    </class>

    <class name="Order" table="orders">
        <id name="Id" column="id">
            <generator class="native"/>
        </id>
        <property name="Date" column="date"/>
        <many-to-one name="Customer" column="customer_id"/>
        <list name="LineItems" table="line_items" lazy="true">
            <key column="order_id"/>
            <index column="line_number"/>
            <composite-element class="LineItem">
                <property name="Quantity" column="quantity"/>
                <many-to-one name="Product" column="product_id"/>
            </composite-element>
        </list>
    </class>

    <class name="Product" table="products">
        <id name="Id" column="id">
            <generator class="native"/>
        </id>
        <property name="SerialNumber" column="serial_number" />
    </class>

</hibernate-mapping>

      请看子表名：Order

官网的例子有个Create_SQL的建表语句，如果你按照这个例子做下去，搞一对多的测试，会发现无论如何都会报错，

嘿嘿，想到原因没？老夫我找了好久才搞明白，浪费了大量脑细胞啊。

      NHibernate中用代码工具生成的实体类必须要将XML映射文件选成嵌入的资源，才可以正常使用。