无法将SQL查询转换为实体框架vb.net

Question

免责声明：可能是长篇

有很多这样的问题，我不太乐意加入这个包，但是， 我有一个包含多行的表，每个行都有效日期，我的SQL查询将根据生效日期获取最新记录

select * from TblTaxmasters

我正在使用此查询来获得所需的结果

select * FROM (select t1.id,t1.shortcode,t1.rev_no,t1.percentage,t1.effectivedate startdate, isnull(MIN(t2.effectivedate),getdate()+1) as enddate FROM tbltaxmaster t1 LEFT
OUTER JOIN tbltaxmaster t2 on t1.id=t2.id AND t1.effectivedate < t2.effectivedate 
GROUP BY t1.id,t1.shortcode,t1.effectivedate,t1.rev_no,t1.percentage ) tx where '2014-05-01' BETWEEN tx.startdate AND tx.enddate 

输出是

现在我正在尝试将此查询转换为vb.net winforms 4.0中的实体框架dbcontext

这是我试过的

Dim tomm = DateTime.Today.AddDays(1)
Dim mydate = DateTime.Today
Dim tax = (From t In (From t1 In tblTaxmasters
                                    From t2 In tblTaxmasters
                                    Where t1.id = t2.id And t1.effectivedate < t2.effectivedate
                                    Select New With {.id = t1.id, .shortcode = t1.shortcode, .maxdate = t1.effectivedate, .mindate = If(t2.effectivedate.HasValue, t2.effectivedate, tomm), .percentage = t1.percentage, .revno = t1.rev_no})
                                Where mydate >= t.mindate And mydate <= t.maxdate Select New With {t.shortcode, t.id, t.percentage, t.revno}).ToList()

它告诉我

  

没有

没有结果，然后我用linqpad尝试了同样的事情，它显示查询执行成功，但没有结果。我检查了sql输出，这里是我得到的

    -- Region Parameters
DECLARE @p0 DateTime = '2014-05-10 00:00:00.000'
DECLARE @p1 DateTime = '2014-05-09 00:00:00.000'
DECLARE @p2 DateTime = '2014-05-09 00:00:00.000'
-- EndRegion
SELECT [t2].[shortcode], [t2].[id], [t2].[percentage], [t2].[rev_no] AS [revno]
FROM (
    SELECT [t0].[id], [t0].[shortcode], [t0].[effectivedate], 
        (CASE 
            WHEN [t1].[effectivedate] IS NOT NULL THEN [t1].[effectivedate]
            ELSE @p0
         END) AS [value], [t0].[percentage], [t0].[rev_no], [t1].[id] AS [id2], [t1].[effectivedate] AS [effectivedate2]
    FROM [tblTaxmaster] AS [t0], [tblTaxmaster] AS [t1]
    ) AS [t2]
WHERE (@p1 >= [t2].[value]) AND (@p2 <= [t2].[effectivedate]) AND ([t2].[id] = [t2].[id2]) AND ([t2].[effectivedate] < [t2].[effectivedate2])

显然是某种东西

  

在翻译中丢失

所以任何人都可以指出我向前迈进的方向。

Answer 1

@Mark，感谢您指出正确的方向，实际上我必须在另一个论坛的this链接的帮助下进行调整。但很高兴两者都成功了，所以这就是我最后所做的事情

Dim tax = From c In ctx.tblTaxmasters
                        Group c By c.id Into g = Group
                    Select g.OrderByDescending(Function(x) x.effectivedate).FirstOrDefault()


            Dim mytax = tax.ToList()

感谢您的帮助

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