通过 NHibernate 中的鉴别器进行查询 [英] Query by discriminator in NHibernate

问题描述

我对此进行了一些搜索，但没有发现任何内容.是否可以创建一个 Hibernate 查询来基于鉴别器返回一组对象?

I did some searching on this and didn't turn up anything. Is it possible to create a Hibernate query to return a set of objects based on a discriminator?

我有一个 AbstractUser 类，它由具体类 UserTypeA 和 UserTypeB 扩展.我正在使用每个层次结构表模型来映射我在 NHibernate 中的类，因此 UserTypeA 和 UserTypeB 都存储在具有不同鉴别器值的同一个表中.这是我的鉴别器映射属性:

I have an AbstractUser class which is extended by the concrete classes UserTypeA and UserTypeB. I'm using the table-per-hierarchy model to map my classes in NHibernate, so UserTypeA and UserTypeB are both stored in the same table with different discriminator values. Here is my discriminator mapping property:

<discriminator column="Type" type="string"/>

我的表中有一个列包含用户类型的名称.我想知道是否可以使用它运行 NHibernate 查询.

I have a column in my table that contains the name of the user type. I'm wondering if it's possible to run a NHibernate query using this.

我试过了:

public IList<DomainBase> FindByType(string typeName, Type type)
{
    string query = "from " + type.Name + " k where k.Type = " + typeName;
    return Session.CreateQuery(query).List<DomainBase>();
}

但由于 Type 实际上不是类的属性，只是表中的一列，这显然行不通.除非有一种方法可以将属性用作鉴别器，否则同时拥有用于此目的的属性和鉴别器似乎是多余的?

But since Type is not actually a property of the class, just a column in the table, this obviously doesn't work. It would seem redundant to have both a property for this purpose and a discriminator, unless there's a way to use a property as a discriminator?

推荐答案

实际上，这在 http://www.nhibernate.info/doc/nh/en/index.html#queryhql-where:

同样，特殊属性class访问一个的鉴别器值多态情况下的实例坚持..Net 类名嵌入在 where 子句中转换为其鉴别器值.

Likewise, the special property class accesses the discriminator value of an instance in the case of polymorphic persistence. A .Net class name embedded in the where clause will be translated to its discriminator value.

 from Eg.Cat cat where cat.class = Eg.DomesticCat

您还可以将 System.Type 实例作为参数传递.

You can also pass a System.Type instance as a parameter.

这篇关于通过 NHibernate 中的鉴别器进行查询的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！