1

就这个问题而言，假设我有一个有多个展品的动物园。每个展览都有自己的时间表和一系列活动，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。当使用带有IEnumerable( session.Query<Exhibit>().AsEnumerable()) 的查询时，它可以正常工作；但是，当我将查询切换到使用IQueryable时，NHibernate 会崩溃。

我已将原始错误的初始来源确定为查询中的一个特定条件：

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

由于该条件本身很长，因此我继续逐步将其分解：

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.

活动上的错误还给出了 NHibernate 尝试生成的 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。

我对这个查询的想法是错误的吗？如果这实际上是 NHibernate 中带有 LINQ lambda 之一的错误，是否有一些解决方法？

更新-请参阅下面的答案

看起来 NHibernate 在确定要加入哪个表以用于.SelectMany(x => x.Activities)

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();
        });
    }
}
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1 回答 1

1

正如@Firo 指出的那样，NHibernate 在我用于自定义集合的组件方面遇到了一些困难。如果您查看问题中的 SQL，您会看到 NHibernate 无法加入Activities表和Departments表以查找关联的负责部门。

我通过切换到 LINQ 查询语法并显式加入表来纠正这个问题。OfType我还通过检查 inline withis和 cast with避免了（同样，最有可能的组件问题）的问题as：

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。如果您遵循此模式并且仍然遇到错误，请尝试更改别名的名称（我喜欢在它们前面添加“temp”—— from tempSchedule in ...、、join tempActivity in ...等）。

于 2013-10-22T12:44:11.160 回答