FirstOrDefault 在比较 DateTime 时在不同的计算机上给出不同的结果？对象

Question

我正在尝试比较 IQueryable 中的两个可为 null 的 DateTime 对象（从数据库中获取），如下所示：

result.FirstOrDefault(x => x.FirstDateTime == secondDateTime)

这在某些开发人员的计算机上可以正确执行，但在我的计算机上却不能。它没有给出任何结果。因为如果我将结果转换为这样的列表，它会起作用：

result.ToList().FirstOrDefault(x => x.FirstDateTime == secondDateTime)

当然我不想留下那样的代码，只是为了表明这不是因为在 IQueryable 中找不到日期

两个值都是 UTC。我尝试使用 Single、SingleOrDefault、First 和 Where，结果都相同。我也试过比较 FirstDateTime.Value 和 secondDateTime.Value。同样，结果相同

IQueryable 的提供程序是

System.Data.Entity.Internal.Linq.DbQueryProvider.

这可能是什么原因造成的？为什么第一段在某些计算机上可以工作，但在其他计算机上却不能，这取决于什么？

这是正在生成的 SQL :

FROM ( SELECT 
[Extent1].[Id] AS [Id], 
[Extent1].[OtherProperty1] AS [OtherProperty1], 
[Extent1].[Version] AS [Version], 
[Extent1].[Submitted] AS [Submitted], 
[Extent1].[SubmittedBy] AS [SubmittedBy], 
[Extent1].[Created] AS [Created], 
[Extent1].[CreatedBy] AS [CreatedBy], 
[Extent2].[Value] AS [Value], 
[Extent2].[OtherProperty2] AS [OtherProperty2], 
[Extent2].[Description] AS [Description], 
[Extent2].[Latitude] AS [Latitude], 
[Extent2].[Longitude] AS [Longitude], 
[Extent2].[OtherProperty3] AS [OtherProperty3], 
[Extent2].[OtherProperty4] AS [OtherProperty4], 
[Extent2].[FirstDateTime] AS [FirstDateTime], 
''0X0X'' AS [C1]
FROM  [dbo].[StructuredInformations] AS [Extent1]
INNER JOIN [dbo].[Positions] AS [Extent2] ON [Extent1].[Id] = [Extent2].[Id]
WHERE ([Extent1].[OtherProperty1] = @p__linq__0) AND ([Extent2].
[FirstDateTime] IS NOT NULL) AND ([Extent2].[FirstDateTime] = @p__linq__1)
)  AS [Project1]
ORDER BY [Project1].[OtherProperty2] DESC, [Project1].[FirstDateTime] ASC,    
[Project1].[Value] ASC',N'@p__linq__0 int,@p__linq__1  
datetime2(7)',@p__linq__0=7,@p__linq__1='2016-10-11 11:45:53.6230000'

Answer 1

IQueryable 不保证顺序。 List<T> 确实如此。要保持 IQueryable 并保持顺序，您应该尝试对 IQueryable 进行排序，而不是尝试获得第一个结果：

result.OrderBy(y => y.FirstDateTime).FirstOrDefault(x => x.FirstDateTime == secondDateTime)

Answer 2

问题类似于this - looks like the LINQ provider generated a datetime value with a fractional second precision of 7 (e.g. 2016-10-11 11:45:53.6230000) while the column in SQL is defined as datetime, which has a precision lower than 7, as opposed to datetime2，可以达到7的精度

要解决此问题，您可以将 SQL 中的列类型从 datetime 更改为 datetime(7)

FirstOrDefault 在比较 DateTime 时在不同的计算机上给出不同的结果？对象

FirstOrDefault giving different results on different computers when comparing DateTime? objects

c#

datetime

iqueryable