Question

出于这个问题的目的，让我们说我有一个有多个展览的动物园。每个展览都有自己的时间表，包括一系列活动，以及负责这些活动的部门和子部门列表。

我有一个相当大的LINQ查询，我用它来获取任何附有员工的展品。将查询与IEnumerable（session.Query<Exhibit>().AsEnumerable()）一起使用时，它可以正常工作;但是，当我将查询切换为使用IQueryable时，NHibernate会崩溃。

我已将查询中原始错误的初始源指向一个特定条件：

var filtered = session.Query<Exhibit>().Where(x => 
    x.AnimalSchedule.Activities
                    .OfType<FeedActivity>()
                    .Any(g => g.ResponsibleDepartment.Manager == employee)         
);

由于这个条件本身很长，我继续一步一步地将其分解出来：

var collection = session.Query<Exhibit>(); // works 
var exhibitAnimalSchedules = collection.Select(x => x.AnimalSchedule); // works                    
var activities = exhibitAnimalSchedules.SelectMany(x => x.Activities); // could not execute query - Incorrect syntax near the keyword 'from'.
var feedActivities = activities.OfType<FeedActivity>(); // Could not find property nor field 'class' in class 'MyProject.Collections.ScheduleActivityCollection'
var filteredFeedActivities = feedActivities.Where(g => g.ResponsibleDepartment.Manager == employee); // Specified method is not supported.

活动上的错误也给出了NHibernate试图生成的SQL：

SELECT 
FROM [dbo].[Exhibits] exhibit0_
INNER JOIN [dbo].[ExhibitAnimalSchedules] exhibitanima1_ ON exhibit0_.AnimalScheduleID = exhibitanima1_.ScheduleID
INNER JOIN [dbo].[Schedules] exhibitanima1_1_ ON exhibitanima1_.ScheduleID = exhibitanima1_1_.[ID]
WHERE exhibit0_.ZooID IS NULL

如果您注意到，NHibernate未能列出SELECT语句中的任何列。

我是否在想这个查询错误的方法？如果这实际上是NHibernate中有一个LINQ lambdas的错误，是否有一些解决方法？

更新 - 请参阅下面的答案

看起来NHibernate在确定.SelectMany(x => x.Activities)

加入哪个表时遇到了一些麻烦

作为参考，以下是所涉及类的所有简化Fluent映射：

public class ExhibitMap : ClassMap<Exhibit>
{
    public ExhibitMap()
    {
        References(p => p.AnimalSchedule).Cascade.All();    
    }
}

public class ScheduleMap : ClassMap<Schedule>
{
    public ScheduleMap()
    {        
        Component(x => x.Activities, m => m {
            var cfg = m.HasMany<ScheduleActivity>(Reveal.Member<ScheduleActivityCollection>("_innerList")).LazyLoad();
            cfg.KeyColumn("ScheduleID").Inverse();
            cfg.ForeignKeyConstraintName("FK_Schedule_Activities");
            cfg.Cascade.AllDeleteOrphan();
        });
    }
}

public class ExhibitAnimalScheduleMap : SubclassMap<ExhibitAnimalSchedule>
{
    public ExhibitAnimalScheduleMap()
    {
        References(x => x.Exhibit).Cascade.None();
    }
}

public class ScheduleActivityMap : ClassMap<ScheduleActivity>
{
    public ScheduleActivityMap()
    {
        References(x => x.Schedule).Cascade.None().Not.LazyLoad();
    }
}

public class FeedActivityMap : SubclassMap<FeedActivity>
{
    public FeedActivityMap()
    {    
        this.References(x => x.ResponsibleDepartment).Cascade.All().Not.LazyLoad();

        Component(x => x.Departments, m => m {
            var cfg = m.HasMany<FeedActivityDepartment>(Reveal.Member<FeedActivityDepartmentCollection>("_innerList")).LazyLoad();
            cfg.KeyColumn("ScheduleID").Inverse();
            cfg.ForeignKeyConstraintName("FK_Schedule_Activities");
            cfg.Cascade.AllDeleteOrphan();
        });
    }
}

Answer 1

正如@Firo指出的那样，NHibernate对我用于自定义集合的组件有一些困难。如果您查看问题中的SQL，您将看到NHibernate无法加入Activities表和Departments表来查找相关的负责部门。

我通过切换到LINQ查询语法并明确加入表来纠正这个问题。我还通过使用OfType进行内联检查并使用is进行投射，避免了as（最常见的组件问题）的问题：

var schedules = from schedule in session.Query<Schedule>()
                join activity in session.Query<ScheduleAcivity>() on schedule equals activity.Schedule
                join department in session.Query<FeedActivityDepartment>() on activity equals department.FeedActivity                        
                where (activity is FeedActivity && (activity as FeedActivity).ResponsibleDepartment.Manager == employee) 
                    || (department != null && department.Employee == employee)
                select schedule;

var exhibits = from exhibit in session.Query<Exhibit>()
               where schedules.Any(x => x == exhibit.AnimalSchedule)                             
               select exhibit;

注意：有时NHibernate对LINQ查询中的别名名称很挑剔。如果你遵循这种模式并且仍然遇到错误，请尝试更改别名的名称（我喜欢在他们面前添加“temp” - from tempSchedule in ...，join tempActivity in ...等。）

使用IQueryable使用Select，SelectMany和OfType查询组件时出现LINQ-to-NHibernate错误

1 个答案: