使用 Fluent NHibernate 连接表

Question

我想使用 FN 在表之间进行连接。但是我得到的输出不是很正确的结果。我的代码：

public class Store
{
    public virtual int Id { get; protected set; }
    public virtual string Name { get; set; }
    public virtual IList<Product> Products { get; protected set; }
    public virtual IList<Employee> Staff { get; protected set; }
    public virtual string FirstName { get; set; }
}

public StoreMap()
{
    Table("store");
    Id(store => store.Id).Column("id").GeneratedBy.Increment();
    Map(store => store.Name).Column("name");

    Join("employee", m =>
    {
        m.Optional();
        m.KeyColumn("store_id");
        m.Map(x => x.FirstName).Column("first_name");
    });
}

var shops = session.QueryOver<Store>().Where(shop => shop.Id == 1).List();

SQL 生成的查询

SELECT  this_.id as id3_0_, 
    this_.name as name3_0_, 
    this_1_.first_name as first2_0_0_ 
FROM store this_ 
left outer join employee 
    this_1_ on this_.id=this_1_.store_id 
WHERE this_.id == 1

如果我只执行这个 SQL 查询，我会得到形式为

的正确结果

id3_0_          name3_0_        first2_0_0_
1               Bargin Basin    Daisy       
1               Bargin Basin    Jack
1               Bargin Basin    Sue

但是如果我通过 FN 进行操作，那么变量 shops 我会得到以下数组：

1               Bargin Basin    Daisy       
1               Bargin Basin    Daisy
1               Bargin Basin    Daisy

我用的是FN version 2.0.1.0，NHibernate 4.0。谢谢

Answer 1

Join(...) 用于一对一关联，但您与 Employee 有一对多关联，因此每个商店的连接 returns 多于一行，NHibernate 始终看到相同的 Id 告诉他这是同一个对象，因此它给你 2 倍相同的引用。

您可能想要的是员工及其商店的投影

class EmploymentDto
{
    public int StoreId { get; set; }
    public string StoreName { get; set; }
    public string FirstName { get; set; }
}

EmploymentDto dto = null;
Employee employee = null;
var employments = session.QueryOver<Store>()
    .Where(shop => shop.Id == 1)
    .JoinAlias(s => s.Staff, () => employee)
    .SelectList(l =>
        l.Select(s => s.Id).WithAlias(() => dto.StoreId)
        l.Select(s => s.Name).WithAlias(() => dto.StoreName)
        l.Select(() => employee.FirstName).WithAlias(() => dto.FirstName)
    .TransformUsing(Transformers.AliasToBean<EmploymentDto>())
    .List<EmploymentDto>();

使用 Fluent NHibernate 连接表

Join on tables using Fluent NHibernate

c#

nhibernate

left-join

fluent