如何部分项目，NHibernate的许多领域的子对象 [英] How to partially project a child object with many fields in nHibernate

问题描述

我有以下NHibernate的查询选择基于其课程ID的课程，然后返回选定字段作为课程对象初始获取和查询，没有问题的执行。

I have the following nHibernate query that select a course based on its course id and then return selected fields for the course object on the initial fetch, and the query executes with no issues.

MatchMode option = ... 
CourseItem courseAlias  = null;
TeacherItem teacherAlias = null;

var query = session.QueryOver<CourseItem>()
    .JoinAlias(c => c.Teacher, () => teacherAlias)
    .Where(c => c.CourseID.IsInsensitiveLike(strNumber, option))
    .SelectList(list => list
               .Select(c => c.CourseID).WithAlias(() => courseAlias.CourseID)
               .Select(c => c.IsActive).WithAlias(() => courseAlias.IsActive)
               .Select(c => c.CourseDesc).WithAlias(() => courseAlias.CourseDesc)
               .Select(c => c.Teacher).WithAlias(() => courseAlias.Teacher))
               .TransformUsing(Transformers.AliasToBean<CourseItem>())
.List<CourseItem>();

我想更进一步的查询只返回部分教师目标，比方说，我只是想返回ID和姓名。所以，我预计名单更新如下：

I wanted to go a step further with the query to only return a partial teacher object, let's say i just wanted to return the ID and Name. So, I updated the projected list to as follows:

var query = session.QueryOver<CourseItem>()
    .JoinAlias(c => c.Teacher, () => teacherAlias)
    .Where(c => c.CourseID.IsInsensitiveLike(strNumber, option))
    .SelectList(list => list
               .Select(c => c.CourseID).WithAlias(() => courseAlias.CourseID)
               .Select(c => c.IsActive).WithAlias(() => courseAlias.IsActive)
               .Select(c => c.CourseDesc).WithAlias(() => courseAlias.CourseDesc)
               .Select(c => c.Teacher.ID).WithAlias(() => courseAlias.Teacher.ID)
               .Select(c => c.Teacher.Name).WithAlias(() => courseAlias.Teacher.Name))
               .TransformUsing(Transformers.AliasToBean<CourseItem>())
.List<CourseItem>();

查询不起作用，因为NHibernate的不知道如何来拆分基于Teacher.ID和Teacher.Name。它是否是可能的任何想法，不要取的整个子对象返回父对象？

我试过下面的查询和它的作品，这是不是我的全部理想的结果。

I've tried the following query and it works this is not my fully desired outcome

var query = session.QueryOver<CourseItem>(() => courseAlias)
    .JoinAlias(() => courseAlias.Teacher, () => teacherAlias)
    .Where(() => courseAlias.CourseID.IsInsensitiveLike(strNumber, option))
    .SelectList(list => list
               .Select(() => courseAlias.CourseID)
               .Select(() => courseAlias.IsActive)
               .Select(() => courseAlias.CourseDesc)
               .Select(() => teacher.ID)
               .Select(() => teacher.Name))
    .List<object[]>();

我可以查询正确的价值观，但无法正确转换回课程/教师的数据类型。

I can query the right values but unable to transform it back correctly to the Course / teacher data type.

有什么想法？

谢谢！

推荐答案

我们的确可以使用自定义变压器。还有一个，这我使用了真是非常非常深的预测的（计有动态对象 - 的 5.1.13。组件，动力组件）的

We can indeed use custom transformer. There is one, which I am using for a really very very deep projections (inlcuding dynamic objects - 5.1.13. component, dynamic-component)

• DeepTransformer＆LT; TEntity＆GT;

把它（如果需要调整），并最终查询可以是这样

Take it (if needed adjust it) and your final query could be like this

// just the last lines are different
var query = session.QueryOver<CourseItem>()
    .JoinAlias(c => c.Teacher, () => teacherAlias)
    .Where(c => c.CourseID.IsInsensitiveLike(strNumber, option))
    .SelectList(list => list
           .Select(c => c.CourseID).WithAlias(() => courseAlias.CourseID)
           .Select(c => c.IsActive).WithAlias(() => courseAlias.IsActive)
           .Select(c => c.CourseDesc).WithAlias(() => courseAlias.CourseDesc)

           // the native WitAlias would not work, it uses expression
           // to extract just the last property
           //.Select(c => c.Teacher.ID).WithAlias(() => courseAlias.Teacher.ID)
           //.Select(c => c.Teacher.Name).WithAlias(() => courseAlias.Teacher.Name))

           // so we can use this way to pass the deep alias
          .Select(Projections.Property(() => teacherAlias.ID).As("Teacher.ID"))
          .Select(Projections.Property(() => teacherAlias.Name).As("Teacher.Name"))

           // instead of this
           // .TransformUsing(Transformers.AliasToBean<CourseItem>())
           // use this
           .TransformUsing(new DeepTransformer<CourseItem>())

和的情况下，你的别名，你匹配的属性名称，该转换器将内置对象树...

And in case, that your aliases do match to property names, that transformer will built the object tree...

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