【发布时间】：2011-07-28 02:44:22
【问题描述】：
在此处输入代码`我有几个使用“let”关键字的 Linq 查询。它们在 3.5 中运行良好，但我在 4.0 中看到了一个非常奇怪的行为。
例子：
var query1 =
(from xVehicleOption in this.entities.VehicleOptionSet
let regionPriceAdjustment = (from xOptionRegionPriceAdjustmentLeftOuter in this.entities.OptionRegionPriceAdjustmentSet
where xOptionRegionPriceAdjustmentLeftOuter.VehicleTypeRegionId == this.vehicleTypeRegionId
&& xOptionRegionPriceAdjustmentLeftOuter.VehicleId == this.vehicleId
&& xOptionRegionPriceAdjustmentLeftOuter.VehicleOptionId == xVehicleOption.VehicleOptionId
select new
{
xOptionRegionPriceAdjustmentLeftOuter,
xOptionRegionPriceAdjustmentLeftOuter.xPriceType
})
where xVehicleOption.VehicleId == this.vehicleId
&& (xVehicleOption.OptionTypeId == 5 || xVehicleOption.OptionTypeId == 7)
select new
{
Name = xVehicleOption.DisplayName,
VehicleOptionId = xVehicleOption.VehicleOptionId,
SortOrder = xVehicleOption.SortOrder,
OptionAvailability = xVehicleOption.OptionAvailabilityDisplayName,
IsDefaultConfiguration = xVehicleOption.IsDefaultConfiguration,
OptionType = xVehicleOption.OptionTypeDisplayName,
RegionPriceAdjustment = regionPriceAdjustment
}).OrderBy(o => o.SortOrder);
这允许枚举 2 个嵌套循环。每个选项一个，一个选项内的每个区域调整一个。
foreach (var bookOption in query)
{
.......
foreach (var regionAdjustment in bookOption.RegionPriceAdjustment)
{
.......
}
}
4.0 中的问题是生成的 SQL 是一个 SELECT FROM RegionPriceAdjustment 表，没有任何 WHERE 子句（使用 Profiler 跟踪）。这意味着命令超时（无论如何都是错误的，因为查询的其他部分没有任何迹象）。
我试图用 .Include 替换“let”，这适用于启用延迟加载，但它会为每个 PriceType 生成一个动态 sql 语句（有 8 个，因此效率不高）。我试图禁用延迟加载，但这肯定会给我一个错误，因为 PriceType 没有被加载。我尝试使用两个 select 分隔为 into，但我遇到了同样的问题。
顺便说一句，在 4.0 中，我将 POCO 和 EntityFramework DLL 与 DbContext 对象一起使用。我没有尝试过使用 ObjectContext，但这不应该有任何区别，因为 DbContext 环绕在 ObjectContext 周围。
关于它为什么这样做的任何线索？有什么建议吗？
谢谢，伊夫
已编辑：
这是 3.5 的 SQL：
[Project2].[VehicleOptionId] AS [VehicleOptionId],
[Project2].[DisplayName] AS [DisplayName],
[Project2].[OptionAvailabilityDisplayName] AS [OptionAvailabilityDisplayName],
[Project2].[IsDefaultConfiguration] AS [IsDefaultConfiguration],
[Project2].[SortOrder] AS [SortOrder],
[Project2].[VehicleOptionId1] AS [VehicleOptionId1],
[Project2].[CategoryId] AS [CategoryId],
[Project2].[CategoryId1] AS [CategoryId1],
[Project2].[DisplayName1] AS [DisplayName1],
[Project2].[C1] AS [C1],
[Project2].[C2] AS [C2],
[Project2].[VehicleOptionId2] AS [VehicleOptionId2],
[Project2].[VehicleTypeRegionId] AS [VehicleTypeRegionId],
[Project2].[VehicleId] AS [VehicleId],
[Project2].[PriceTypeId] AS [PriceTypeId],
[Project2].[PriceAdjustment] AS [PriceAdjustment],
[Project2].[ValueTypeId] AS [ValueTypeId],
[Project2].[PriceTypeId1] AS [PriceTypeId1],
[Project2].[DisplayName2] AS [DisplayName2]
FROM ( SELECT
[Extent1].[VehicleOptionId] AS [VehicleOptionId],
[Extent1].[DisplayName] AS [DisplayName],
[Extent1].[OptionAvailabilityDisplayName] AS [OptionAvailabilityDisplayName],
[Extent1].[IsDefaultConfiguration] AS [IsDefaultConfiguration],
[Extent1].[SortOrder] AS [SortOrder],
[Extent2].[VehicleOptionId] AS [VehicleOptionId1],
[Extent2].[CategoryId] AS [CategoryId],
[Extent3].[CategoryId] AS [CategoryId1],
[Extent3].[DisplayName] AS [DisplayName1],
1 AS [C1],
[Project1].[VehicleOptionId] AS [VehicleOptionId2],
[Project1].[VehicleTypeRegionId] AS [VehicleTypeRegionId],
[Project1].[VehicleId] AS [VehicleId],
[Project1].[PriceTypeId] AS [PriceTypeId],
[Project1].[PriceAdjustment] AS [PriceAdjustment],
[Project1].[ValueTypeId] AS [ValueTypeId],
[Project1].[PriceTypeId1] AS [PriceTypeId1],
[Project1].[DisplayName] AS [DisplayName2],
[Project1].[C1] AS [C2]
FROM [dbo].[KBB_V3_VehicleOption] AS [Extent1]
INNER JOIN [dbo].[KBB_V3_VehicleOptionCategory] AS [Extent2] ON ([Extent1].[VehicleOptionId] = [Extent2].[VehicleOptionId]) OR (([Extent1].[VehicleOptionId] IS NULL) AND ([Extent2].[VehicleOptionId] IS NULL))
INNER JOIN [dbo].[KBB_V3_Category] AS [Extent3] ON ([Extent2].[CategoryId] = [Extent3].[CategoryId]) OR (([Extent2].[CategoryId] IS NULL) AND ([Extent3].[CategoryId] IS NULL))
LEFT OUTER JOIN (SELECT
[Extent4].[VehicleOptionId] AS [VehicleOptionId],
[Extent4].[VehicleTypeRegionId] AS [VehicleTypeRegionId],
[Extent4].[VehicleId] AS [VehicleId],
[Extent4].[PriceTypeId] AS [PriceTypeId],
[Extent4].[PriceAdjustment] AS [PriceAdjustment],
[Extent4].[ValueTypeId] AS [ValueTypeId],
[Extent5].[PriceTypeId] AS [PriceTypeId1],
[Extent5].[DisplayName] AS [DisplayName],
1 AS [C1]
FROM [dbo].[KBB_V3_OptionRegionPriceAdjustment] AS [Extent4]
LEFT OUTER JOIN [dbo].[KBB_V3_PriceType] AS [Extent5] ON [Extent4].[PriceTypeId] = [Extent5].[PriceTypeId] ) AS [Project1] ON ([Project1].[VehicleTypeRegionId] = @p__linq__6) AND ([Project1].[VehicleId] = @p__linq__7) AND ([Project1].[VehicleOptionId] = [Extent1].[VehicleOptionId])
WHERE (4 = [Extent1].[OptionTypeId]) AND ([Extent1].[VehicleId] = @p__linq__9) AND (22 = [Extent3].[CategoryTypeId])
) AS [Project2]
ORDER BY [Project2].[SortOrder] ASC, [Project2].[VehicleOptionId] ASC, [Project2].[VehicleOptionId1] ASC, [Project2].[CategoryId] ASC, [Project2].[CategoryId1] ASC, [Project2].[C2] ASC',N'@p__linq__6 int,@p__linq__7 int,@p__linq__9 int',@p__linq__6=0,@p__linq__7=261637,@p__linq__9=261637
这是我仅在 4.1 中得到的（使用 POCO）：
SELECT
[Extent1].[VehicleOptionId] AS [VehicleOptionId],
[Extent1].[VehicleTypeRegionId] AS [VehicleTypeRegionId],
[Extent1].[VehicleId] AS [VehicleId],
[Extent1].[PriceTypeId] AS [PriceTypeId],
[Extent1].[PriceAdjustment] AS [PriceAdjustment],
[Extent1].[ValueTypeId] AS [ValueTypeId]
FROM [dbo].[KBB_V3_OptionRegionPriceAdjustment] AS [Extent1]
如您所见，没有 WHERE 子句，也没有其他 SQL 的踪迹......
【问题讨论】：
标签： linq-to-entities