database - 如何在 NHibernate 中进行此投影？

Question

我的数据库中有这些实体

对于给定的Job，我想基本上得到以下形式的结果

<Translation>,<ExternalUnit.Text>,<ExternalTranslation.Text>

加入条件是 Translation.Unit.Text == ExternalUnit.Text

这是我目前所拥有的，工作正常:

var props = session.QueryOver<Translation>(() => translation)
            .Select(c => translation.Id, c => externalUnit.Text, c => externalTranslation.Text)
            .JoinAlias(() => translation.TranslationUnit, () => unit)                
            .JoinAlias(() => unit.Job, () => job)
            .Where(() => unit.Job == job)
            .JoinAlias(() => job.ExternalUnits, () => externalUnit)
            .JoinAlias(() => externalUnit.ExternalTranslations, () => externalTranslation)
            .Where(() => externalUnit.Text == unit.Text)
            .List<object[]>();

var translations = session.QueryOver<Translation>(() => translation)                
            .JoinAlias(() => translation.TranslationUnit, () => unit)                
            .JoinAlias(() => unit.Job, () => job)
            .Where(() => unit.Job == job)
            .JoinAlias(() => job.ExternalUnits, () => externalUnit)
            .JoinAlias(() => externalUnit.ExternalTranslations, () => externalTranslation)
            .Where(() => externalUnit.Text == unit.Text)
            .List<Translation>()
            .ToList();

然后我遍历 translations，引用 props。但是，我不喜欢这种方法，因为我不必要地对数据库执行了两个(几乎相同的)查询，而不是一个。

但我无法获得所需的投影。我在想这样的事情:

var data = session.QueryOver<Translation>(() => translationAlias)                
            .JoinAlias(() => translation.TranslationUnit, () => unit)                
            .JoinAlias(() => unit.Job, () => job)
            .Where(() => unit.Job == job)
            .JoinAlias(() => job.ExternalUnits, () => externalUnit)
            .JoinAlias(() => externalUnit.ExternalTranslations, () => externalTranslation)
            .Where(() => externalUnit.Text == unit.Text)
            .Select(() => translation, () => externalUnit.Text, () => externalTranslation.Text)
            .List()

但是，显然，NHibernate 不喜欢 Select(() => translation...) 位(它不允许我投影整个实体)。

理想情况下我想选择匿名类型，比如

var data = session.QueryOver<Translation>()
             ...
             .Select(() => new { A = translation, B = externalTranslation })

但我想 NHibernate 目前还没有...

非常感谢您的任何建议。

Answer 1

我知道了! NHibernate 的 LINQ 提供者救了我。它的优点在于它可以选择匿名类型，这使得加入变得非常容易。以防万一有人好奇，这是针对我的特殊情况:

var q = 
(from c in
  (from b in            
    (from translation in session.Query<Translation>()
     join unit in units on translation.Unit equals unit
     where unit.Job == job
     select new { Translation = translation, Original = unit.Text })         
   join extUnit in externalUnits on job equals extUnit.Job
   where extUnit.Text == b.Original
   select new { Translation = b.Translation, ExternalUnit = extUnit })
 join extTranslation in extTranslations on c.ExternalUnit equals extTranslation.Unit
 select new { Translation = c.Translation, Suggestion = extTranslation })
 .ToList();

它生成的SQL很合理，我很高兴:)