在这里输入代码。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。
示例：
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，一个选项中每个区域调整一个。
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，因为没有查询其他部分的迹象）。
我试图通过.Include替换“let”，这适用于启用延迟加载，但它为每个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给我一个错误，因为PriceType没有加载。我试过使用两个选择分隔成但我得到同样的问题。
在4.0中BTW，我正在使用POCO和EntityFramework DLL与DbContext对象。我没有尝试使用ObjectContext，但是由于DbContext包装了ObjectContext，所以不应该有任何区别。
为什么会这样做的任何线索？有什么建议吗？
谢谢，Yves
编辑：
以下是带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
这是我唯一得到的4.1（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，也没有其余SQL的跟踪......
答案 0 :(得分：0)
我找到了一个解决方法。我的新查询如下：
var query =
(from xVehicleOption in this.entities.VehicleOptionSet
let regionPriceAdjustment = (from xOptionRegionPriceAdjustmentLeftOuter in xVehicleOption.XOptionRegionPriceAdjustment
where xOptionRegionPriceAdjustmentLeftOuter.VehicleTypeRegionId == this.vehicleTypeRegionId
//&& xOptionRegionPriceAdjustmentLeftOuter.VehicleId == this.vehicleId
//&& xOptionRegionPriceAdjustmentLeftOuter.VehicleOptionId == xVehicleOption.VehicleOptionId
select new
{
xOptionRegionPriceAdjustmentLeftOuter,
xOptionRegionPriceAdjustmentLeftOuter.XPriceType
})
join xVehicleOptionCategory in this.entities.VehicleOptionCategorySet on xVehicleOption.VehicleOptionId equals xVehicleOptionCategory.VehicleOptionId
join xCategory in this.entities.CategorySet on xVehicleOptionCategory.CategoryId equals xCategory.CategoryId
where xVehicleOption.VehicleId == this.vehicleId
&& xVehicleOption.OptionTypeId == 4
&& xCategory.CategoryTypeId == 22
select new
{
Name = xVehicleOption.DisplayName,
VehicleOptionId = xVehicleOption.VehicleOptionId,
SortOrder = xVehicleOption.SortOrder,
OptionAvailability = xVehicleOption.OptionAvailabilityDisplayName,
IsDefaultConfiguration = xVehicleOption.IsDefaultConfiguration,
OptionType = xCategory.DisplayName,
RegionPriceAdjustment = regionPriceAdjustment
}).OrderBy(o => o.SortOrder);
请注意我在第三行查询xVehicleOption而不是this.entities。因此进行内连接。当然，我不需要现在注释掉的行。我在阅读Craig Stuntz的优秀文章时找到了这个解决方案：
http://blogs.teamb.com/craigstuntz/2010/01/13/38525/
当然，根据Craig的说法，我的查询可以更简化，但我想保留大部分内容，因为它是出于可理解的原因。
这仍然无法解释为什么原始查询在4.1中不起作用（同样，where语句被完全忽略），但这是一种可接受的快速解决方法。
希望这有助于其他人，YC