如何在 Linq Query 中选择最小和最大日期值 [英] How to Select Min and Max date values in Linq Query

问题描述

我正在从 SQL 迁移到 Linq，我需要一些帮助.我正在测试 Linq-to-SQL 和 Linq-to-Entities.我想尝试两种方法来决定哪一种最适合我.感谢您的帮助.谢谢

I am moving from SQL to Linq and I need some help. I am testing both Linq-to-SQL and Linq-to-Entities. I want to try both to decide which one suits me best. Your help is appreciated. Thanks

从表中选择最小日期值的正确语法是什么(如果可能，在 vb.net 中)?

What is the correct syntax (in vb.net if possible) to select the minimum date value from a table?

Dim mydata As New DataClassesDataContext
Dim myresult = From cv In mydata.T1s
                       Select cv.DATE1, cv.Date2, cv.Datex
myresult=Dump()

我试过我试过用

Select amin=cv.DATE1.Min(), amax=cv.Date1.Max(), bmin=cv.Date2.Min(), etc....

出现这个错误'Min'不是'Date'的成员.

我想获取最小值和最大值的数据如下:

The Data That I want to get min and max on is below:

IOrderedQueryable<VB$AnonymousType_0<DateTime,DateTime>> (16 items) 

Date1                   Date2
17/Oct/09 12:00:00 AM   23/Oct/09 12:00:00 AM
10/Jan/09 12:00:00 AM   15/Feb/09 12:00:00 AM
27/Mar/09 12:00:00 AM   27/Mar/09 12:00:00 AM
30/May/09 12:00:00 AM   30/May/09 12:00:00 AM
25/Jan/09 12:00:00 AM   25/Mar/09 12:00:00 AM
01/Nov/09 12:00:00 AM   01/Nov/09 12:00:00 AM
21/Feb/09 12:00:00 AM   04/Mar/09 12:00:00 AM
02/Mar/09 12:00:00 AM   09/Mar/09 12:00:00 AM
07/Jul/09 12:00:00 AM   07/Jul/09 12:00:00 AM
27/Sep/09 12:00:00 AM   27/Sep/09 12:00:00 AM
05/Nov/09 12:00:00 AM   05/Nov/09 12:00:00 AM
15/Apr/09 12:00:00 AM   15/Apr/09 12:00:00 AM
08/Jun/09 12:00:00 AM   08/Jun/09 12:00:00 AM
07/Jul/09 12:00:00 AM   07/Jul/09 12:00:00 AM
30/Jul/09 12:00:00 AM   30/Jul/09 12:00:00 AM
04/Nov/09 12:00:00 AM   04/Nov/09 12:00:00 AM

现在解决了，但这不是一个完美的解决方案，看来我需要对需要聚合函数的每一列进行单独的查询:

Now resolved, but this is not a the perfect solution, it seems that I needed to do a seperate query for each column that requires aggreagate function :

Sub Main

Dim mm = (From cv In T1s 
Select Datez = (cv.Date1)).Min()

Dim mm1 = (From cv In T1s 
Select Datez = (cv.Date1)).Max()

Dim mm2 = (From cv In T1s 
Select Datez = (Date2)).Min()

Dim mm3 = (From cv In T1s 
Select Datez = (Date2)).Max()
mm.dump()
mm1.dump()
mm2.dump()
mm3.dump()

End Sub

结果如下

10/Jan/09 12:00:00 AM
05/Nov/09 12:00:00 AM
15/Feb/09 12:00:00 AM
05/Nov/09 12:00:00 AM

推荐答案

这应该适合你

//Retrieve Minimum Date
var MinDate = (from d in dataRows select d.Date).Min();

//Retrieve Maximum Date
var MaxDate = (from d in dataRows select d.Date).Max(); 

(来自此处)

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