如何在nHibernate中部分地投影具有许多字段的子对象

我有以下nHibernate查询，它根据其课程ID 选择课程，然后在初始提取时返回课程对象的选定字段 ，并且查询执行时没有任何问题。

MatchMode option = ... CourseItem courseAlias = null; TeacherItem teacherAlias = null; var query = session.QueryOver() .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()) .List(); 

我想进一步查询只返回部分教师对象，假设我只想返回ID和名称。 所以，我将预计列表更新为：

 var query = session.QueryOver() .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()) .List(); 

查询不起作用，因为nHibernate不知道如何根据Teacher.ID和Teacher.Name重新调用。 是否有可能不将整个子对象提取回父对象？

我已经尝试了以下查询，它的工作原理并非我完全想要的结果

 var query = session.QueryOver(() => 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(); 

我可以查询正确的值但无法将其正确转换回课程/教师数据类型。

有什么想法吗？

谢谢！

Answer 1

我们确实可以使用定制变压器。 有一个，我用于非常非常深的投影（包括动态对象 – 5.1.13。组件，动态组件 ）

• DeepTransformer

拿它（如果需要调整它），你的最终查询可能是这样的

 // just the last lines are different var query = session.QueryOver() .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()) // use this .TransformUsing(new DeepTransformer()) 

如果您的别名与属性名称匹配，那么变换器将构建对象树…