通过子级中的parentId对NHibernate进行分组，并从此parentId的父表中获取值

// 定义实体类
public class ParentEntity
{
    public virtual int Id { get; set; }
    public virtual string Value { get; set; }
    public virtual IList<ChildEntity> Children { get; set; }
}

public class ChildEntity
{
    public virtual int Id { get; set; }
    public virtual string Value { get; set; }
    public virtual ParentEntity Parent { get; set; }
}

// NHibernate映射文件
<class name="ParentEntity" table="parent_table">
    <id name="Id" column="id">
        <generator class="native" />
    </id>
    <property name="Value" column="value" />

    <bag name="Children" inverse="true" cascade="all">
        <key column="parent_id" />
        <one-to-many class="ChildEntity" />
    </bag>
</class>

<class name="ChildEntity" table="child_table">
    <id name="Id" column="id">
        <generator class="native" />
    </id>
    <property name="Value" column="value" />

    <many-to-one name="Parent" class="ParentEntity" column="parent_id" />
</class>

// 查询代码
var session = sessionFactory.OpenSession();
var result = session.QueryOver<ChildEntity>()
    .JoinQueryOver(x => x.Parent)
    .Where(x => x.Parent.Id == parentId)
    .List();

// 遍历结果
foreach (var child in result)
{
    var parentValue = child.Parent.Value;
    // 处理逻辑
}