SQL into LINQ ...需要在正確的方向微調

Question

我想使用LINQ作爲DataGrivdView數據源...我有正確的SQL查詢，但我有一段時間重寫它在LINQ ...

SQL：

SELECT ICITEM.ITEMNO, ICITEM.[DESC], MAX(PORCPL.DTARRIVAL) AS Expr1 
FROM ICITEM INNER JOIN 
     PORCPL ON PORCPL.ITEMNO = ICITEM.ITEMNO 
WHERE (ICITEM.ITEMNO LIKE '%R001%') 
GROUP BY ICITEM.ITEMNO, ICITEM.[DESC] 

我在LINQ愚蠢的嘗試（S）：

Dim s = From items In db.ICITEMs 
    Where items.ITEMNO.Contains(Me.txtQuery.Text) Or items.DESC.Contains(Me.txtQuery.Text) 
    Join recDates In db.PORCPLs On items.ITEMNO Equals recDates.ITEMNO 
    Select [Item_ID] = items.ITEMNO, [Description] = items.DESC, [rd] = recDates.DTARRIVAL 

我的LINQ日誌...

SELECT [t0].[ITEMNO] AS [Item_ID], [t0].[DESC] AS [Description], [t1].[DTARRIVAL] AS [rd] 
FROM [dbo].[ICITEM] AS [t0] 
INNER JOIN [dbo].[PORCPL] AS [t1] ON [t0].[ITEMNO] = [t1].[ITEMNO] 
WHERE ([t0].[ITEMNO] LIKE @p0) OR ([t0].[DESC] LIKE @p1) 
-- @p0: Input VarChar (Size = 8000; Prec = 0; Scale = 0) [%r001%] 
-- @p1: Input VarChar (Size = 8000; Prec = 0; Scale = 0) [%r001%] 
-- Context: SqlProvider(Sql2008) Model: AttributedMetaModel Build: 4.0.30319.1 

我無法弄清楚如何在[rd]字段上獲得Max函數......任何見解都將非常感謝。

Answer 1

您需要新增一個Group By。 下面是一個例子，這應有助於：

Dim s = From items In db.ICITEMs 
Where items.ITEMNO.Contains(Me.txtQuery.Text) Or items.DESC.Contains(Me.txtQuery.Text) 
Join recDates In db.PORCPLs On items.ITEMNO Equals recDates.ITEMNO 
Group By items.ITEMNO, items.DESC Into MaxArrivalDate = Max(recDates.DTARRIVAL) 
Select [Item_ID] = items.ITEMNO, [Description] = items.DESC, [rd] = MaxArrivalDate 

Answer 2

你在你的LINQ查詢有一個額外的Contains。如果這是正確的，這裏是完整的LINQ查詢與組by和max：

Dim s = From items In db.ICITEMs 
Where items.ITEMNO.Contains(Me.txtQuery.Text) Or items.DESC.Contains(Me.txtQuery.Text) 
Join recDates In db.PORCPLs On items.ITEMNO Equals recDates.ITEMNO 
Group By items.ITEMNO, items.DESC Into Group 
Let MaxArrival = Group.Max(Function(p) p.recDates.DTARRIVAL) 
Select [Item_ID] = ITEMNO, [Description] = DESC, [rd] = MaxArrival