我試圖創建一個LINQ查詢,這將產生相同的結果,因爲這SQL實例:LINQ GROUP BY /選擇 - 對象引用不設置到對象
SELECT Priority.PriorityKey, Count(Priority.PriorityKey) AS NewPresentingUnits
FROM Priority INNER JOIN SupportPeriod ON Priority.PriorityCode = SupportPeriod.PriorityCode
WHERE (((SupportPeriod.NewClient)=True) AND ((SupportPeriod.DateAssistanceRequested) Between #1/1/2013# And #2/1/2013#) AND ((SupportPeriod.DateFinished) Between #1/1/9999# And #12/31/9999#))
GROUP BY Priority.PriorityKey;
我得到以下結果當我運行SQL查詢:
https://docs.google.com/file/d/0B6b_N7sDgjmvRlBtT1lZWURERVU/edit?usp=sharing
這是LINQ聲明:
SupportPeriodTableAdapter spTa = new SupportPeriodTableAdapter();
SupportPeriodDataTable dataTables = spTa.GetData();
var test = (from sp in dataTables
where (sp.NewClient == true) &&
(sp.DateAssistanceRequested >= new DateTime(2013, 1, 1) &&
sp.DateAssistanceRequested <= new DateTime(2013, 2, 1)) &&
(sp.DateFinished > new DateTime(2013, 2, 1))
group sp by sp.PriorityRow.PriorityKey into groupz
select new { Key = groupz.Key, sount = groupz.Count() });
當我嘗試調試var test
時,我在結果視圖中將「對象引用未設置爲對象的實例」。
https://docs.google.com/file/d/0B6b_N7sDgjmvdGp0bjJCNkE3TTg/edit?usp=sharing
我是新來使用「GROUP BY」和「選擇新的」 LINQ的功能,因此我有一個很難搞清楚了這一點....
'sp.PriorityRow'可能是罪魁禍首 – NSGaga 2013-04-08 01:15:24
@NSGaga SupportPeriod表中的所有FK在Priority表中都有一個有效的PK ...你的意思是我應該使用多個查詢而不使用sp.PriorityRow? – zaza 2013-04-08 01:20:23