Question

我在Linq to NHibernate查询中通过多个字段进行排序时遇到问题。有没有人知道可能出现的问题或是否有解决方法？

代码：

IQueryable<AgendaItem> items = _agendaRepository.GetAgendaItems(location)
   .Where(item => item.Minutes.Contains(query) || item.Description.Contains(query));

int total = items.Count();

var results = items
   .OrderBy(item => item.Agenda.Date)
   .ThenBy(item => item.OutcomeType)
   .ThenBy(item => item.OutcomeNumber)
   .Skip((page - 1)*pageSize)
   .Take(pageSize)
   .ToArray();

return new SearchResult(query, total, results);

我尝试用多个OrderBy调用替换ThenBy。结果相同。如果我注释掉两个ThenBy调用，该方法效果很好。

我收到错误：

    [SqlException (0x80131904): Invalid column name '__hibernate_sort_expr_0____hibernate_sort_expr_1__'.
    Invalid column name '__hibernate_sort_expr_0____hibernate_sort_expr_1__'.]
       System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection) +1948826
       System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) +4844747
       System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) +194
       System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) +2392

    [ADOException: could not execute query
    [ SELECT this_.Id as Id5_2_, this_.AgendaId as AgendaId5_2_, this_.Description as Descript3_5_2_, this_.OutcomeType as OutcomeT4_5_2_, this_.OutcomeNumber as OutcomeN5_5_2_, this_.Minutes as Minutes5_2_, agenda1_.Id as Id2_0_, agenda1_.LocationId as LocationId2_0_, agenda1_.Date as Date2_0_, location2_.Id as Id7_1_, location2_.Name as Name7_1_ FROM AgendaItem this_ left outer join Agenda agenda1_ on this_.AgendaId=agenda1_.Id left outer join Location location2_ on agenda1_.LocationId=location2_.Id WHERE location2_.Id = ? and (this_.Minutes like ? or this_.Description like ?) ORDER BY agenda1_.Date asc, this_.OutcomeType asc, this_.OutcomeNumber asc ]
    Positional parameters:  #0>1 #0>%Core% #0>%Core%
    [SQL: SELECT this_.Id as Id5_2_, this_.AgendaId as AgendaId5_2_, this_.Description as Descript3_5_2_, this_.OutcomeType as OutcomeT4_5_2_, this_.OutcomeNumber as OutcomeN5_5_2_, this_.Minutes as Minutes5_2_, agenda1_.Id as Id2_0_, agenda1_.LocationId as LocationId2_0_, agenda1_.Date as Date2_0_, location2_.Id as Id7_1_, location2_.Name as Name7_1_ FROM AgendaItem this_ left outer join Agenda agenda1_ on this_.AgendaId=agenda1_.Id left outer join Location location2_ on agenda1_.LocationId=location2_.Id WHERE location2_.Id = ? and (this_.Minutes like ? or this_.Description like ?) ORDER BY agenda1_.Date asc, this_.OutcomeType asc, this_.OutcomeNumber asc]]
       NHibernate.Loader.Loader.DoList(ISessionImplementor session, QueryParameters queryParameters) +258
       NHibernate.Loader.Loader.ListIgnoreQueryCache(ISessionImplementor session, QueryParameters queryParameters) +18
       NHibernate.Loader.Loader.List(ISessionImplementor session, QueryParameters queryParameters, ISet`1 querySpaces, IType[] resultTypes) +87
       NHibernate.Impl.SessionImpl.List(CriteriaImpl criteria, IList results) +342
       NHibernate.Impl.CriteriaImpl.List(IList results) +41
       NHibernate.Impl.CriteriaImpl.List() +35
       NHibernate.Linq.CriteriaResultReader`1.List() in C:\home\dev\tools\NHibernate\NHibernateContribSrc\src\NHibernate.Linq\src\NHibernate.Linq\CriteriaResultReader.cs:22
       NHibernate.Linq.d__0.MoveNext() in C:\home\dev\tools\NHibernate\NHibernateContribSrc\src\NHibernate.Linq\src\NHibernate.Linq\CriteriaResultReader.cs:27

Answer 1

这对我来说就像Linq到NHybernate的一个错误。一种可能的解决方法是在排序之前转换为数组。一个潜在的重大缺点是你不能在枚举之前使用Skip（）和Take（）来限制结果，所以这对你来说可能还不够。

var results = items
   .ToArray()
   .OrderBy(item => item.Agenda.Date)
   .ThenBy(item => item.OutcomeType)
   .ThenBy(item => item.OutcomeNumber)
   .Skip((page - 1)*pageSize)
   .Take(pageSize)

Answer 2

虽然我不认为它会有所作为，如果你像这样做你的linq会发生什么：

（来自i in in order orderby i.prop1，i.prop2，i.prop3）.Skip（...）。Take（...）。ToArray（）;

Answer 3

如果结果集相对较小，则可以将其首先转换为数组可能是可接受的解决方案。但是，如果您想让SQL Server来完成这项工作，则最好采用以下方式：

var results = items
   .OrderBy(item => item.Agenda.Date).Asc
   .ThenBy(item => item.OutcomeType).Asc
   .ThenBy(item => item.OutcomeNumber).Asc
   .Skip((page - 1)*pageSize)
   .Take(pageSize)
   .ToArray();

无论何时在Linq的NHibernate方言中使用OrderBy或OrderByAlias方法时，都应始终添加Asc或Desc修饰符。

Linq to NHibernate多个OrderBy调用

3 个答案: