NHibernate:QueryOver<>帮助 [英] NHibernate: QueryOver<> help

问题描述

我刚开始使用NHibernate，但是在运行更复杂的查询时遇到了麻烦.

I'm just starting out with NHibernate and I'm having trouble with running more complex queries.

我有一些带有附加标签列表的实体.用户将提供两个标签列表，包括和排除.

I have entities with a list of tags attached. The user will provide two lists of tags, include and exclude.

我需要找到具有所有include标记的所有实体，并在排除列表中排除具有任何标记的所有实体.

I need to find all the entities that have all of the include tags, and exclude any entites that have any tag in the exclude list.

下面是我的第一项努力-这显然是错误的，因为它列出了所有具有任何包含标签而不是全部包含标签的Display对象！

Below is my first effort- which is clearly wrong as its listing all Display objects that have any of the include tags rather than all!

非常感谢任何帮助.

var includeTagIds = (from tag in regime.IncludeTags select tag.Id).ToList<int>();
var excludeTagIds = from tag in regime.ExcludeTags select tag.Id;


var displays = session.QueryOver<Display>()
                      .JoinQueryOver<DisplayTag>(display => display.Tags)
                      .WhereRestrictionOn(tag => tag.Id)
                      .IsIn(includeTagIds).List().Distinct();


return displays.ToList();

推荐答案

该查询并非易事(请考虑如何使用原始SQL进行此操作).我认为以下方法会起作用(需要两个相关的子查询):

That query isn't trivial (have a think about how you might do this using raw SQL). I think the following will work (requiring two correlated sub-queries):

Display displayAlias = null;

var countIncludedTagsSubquery =
    QueryOver.Of<Display>()
        .Where(d => d.Id == displayAlias.Id)
        .JoinQueryOver<DisplayTag>(d => d.Tags)
            .WhereRestrictionOn(t => t.Id).IsInG(includedTagIds)
            .Select(Projections.RowCount());

var excludedTagsSubquery =
    QueryOver.Of<Display>()
        .Where(d => d.Id == displayAlias.Id)
        .JoinQueryOver<DisplayTag>(d => d.Tags)
            .WhereRestrictionOn(t => t.Id).IsInG(excludedTagIds)
            .Select(t => t.Id);

var displays =
    session.QueryOver<Display>(() => displayAlias)
        .WithSubquery.WhereValue(includedTagIds.Count).Eq(countIncludedTagsSubquery)
        .WithSubquery.WhereNotExists(excludedTagsSubquery)
        .List();

这篇关于NHibernate:QueryOver<>帮助的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！