Question

关于Linq To Entity的排序问题

IQueryable.Where(e => e.IsTrash == flag).ToList();
IQueryable.Where(e => e.IsTrash == flag).OrderBy(e => e.Sort).ToList();
为什么一排序就会多SELECT一次，语句如下：

exec sp_executesql N'SELECT
[Project1].[RowID] AS [RowID],
[Project1].[Code] AS [Code],
[Project1].[Sort] AS [Sort],
FROM ( SELECT
[Extent1].[RowID] AS [RowID],
[Extent1].[Code] AS [Code],
[Extent1].[Sort] AS [Sort],
FROM [dbo].[Language] AS [Extent1]
WHERE [Extent1].[IsTrash] = @p__linq__0
) AS [Project1]
ORDER BY [Project1].[Sort] ASC',N'@p__linq__0 bit',@p__linq__0=0
go
===========================================
如果参数直接写死，也没问题。
比如将布尔值参数flag直接写为false：
IQueryable.Where(e => e.IsTrash == false).OrderBy(e => e.Sort).ToList();
这样也只SELECT 1次

Answer 1

EF直接转换的SQL就是这样子的，对于性能的影响是一样的。

参见下图