NHibernate QueryOver 关联不包含项目答案

【问题标题】：NHibernate QueryOver association does not contain itemNHibernate QueryOver 关联不包含项目
【发布时间】：2011-09-10 07:09:05
【问题描述】：

有人可以帮我将 LINQ 表达式转换为 Nhibernate QueryOver

from m in messages
where !m.Recipients.Any(rcpt => rcpt.IsDeleted && rcpt.User = user)

我试过了

var qry = Session.QueryOver<UserMessage>();
qry.Where(m => m.Recipients.Any(r => !r.IsDeleted && r.User == user));

但是得到了

System.Exception : 无法识别的方法调用：System.Linq.Enumerable:Boolean Any[TSource](System.Collections.Generic.IEnumerable1[TSource], System.Func2[TSource,System.Boolean]

【问题讨论】：

标签： nhibernate queryover

【解决方案1】：

!m.Recipients.Any(...) 转换为“不存在”子查询。您将需要几个别名来将子查询与主查询相关联，并且子查询需要有一个投影才能使 NHibernate 满意。

试试这样的：

UserMessage messageAlias = null;
UserMessage recipientMessageAlias = null;

var subquery = QueryOver.Of<MessageRecipient>()
    .JoinAlias(x => x.Message, () => recipientMessageAlias)
    .Where(x => x.IsDeleted == true) // your criteria
    .Where(x => x.User.Id == userId)
    .Where(() => recipientMessageAlias.Id == messageAlias.Id) // correlated subquery
    .Select(x => x.Id); // projection

var query = session.QueryOver(() => messageAlias)
    .Where(Subqueries.WhereNotExists(subquery));

return query.List();

【讨论】：

【解决方案2】：

我是这样做到的：

UserMessage messageAlias = null;

var qry = Session.QueryOver<UserMessage>(() => messageAlias);

UserMessageRecipient recipientAlias = null;

var deletedbyUser = QueryOver.Of(() => recipientAlias)
  .Select(x => x.Id)
  .Where( () => recipientAlias.Message.Id == messageAlias.Id
    && (recipientAlias.Recipient == query.User && recipientAlias.IsDeleted))
                .DetachedCriteria;
qry.Where(Subqueries.NotExists(deletedbyUser));

【讨论】：

【解决方案3】：

尝试使用带有 session.Query 而不是 QueryOver 的 Linq 版本

var qry = Session.Query<UserMessage>();
qry.Where(m => m.Recipients.Any(r => !r.IsDeleted && r.User == user));

【讨论】：