選擇計算字段

Question

如何選擇實體框架中兩個字段之間的差異作爲持續時間。以下是相應的SQL查詢：

SELECT InitiateTime, StartTime, EndTime, Ano,Bno, datediff(s,StartTime,EndTime) as duration 
FROM [NEPALIVR2].[dbo].[CDR] 
WHERE StartTime >= startDate and StartTime <= endDate order by StartTime desc 

LINQ

from u in db.CDRs 
where u.InitiateTime >= startDate && u.InitiateTime <= endDate 
orderby u.InitiateTime descending 
select new 
{ 
    InitiateTime = u.InitiateTime, 
    StartTime = u.StartTime, 
    EndTime = u.StartTime, 
    Ano = u.Ano, 
    Bno = u.Bno, 
    Duration = (SqlFunctions.DateDiff("mi", u.StartTime, u.EndTime))/360, 
}; 

這將返回錯誤：喜歡你的問題

Cannot implicitly convert type 'System.Linq.IQueryable<AnonymousType#1>' to 'System.Linq.IQueryable<IVRControlPanel.Models.CDR>' . An explicit conversion exists (are you missing a cast?)

Answer 1

看起來不差計算，但在匿名類型你是從查詢返回。將其更改爲CDR對象：

select new CDR 
{ 
    InitiateTime = u.InitiateTime, 
    StartTime = u.StartTime, 
    EndTime = u.StartTime, 
    Ano = u.Ano, 
    Bno = u.Bno, 
    Duration = SqlFunctions.DateDiff("mi", u.StartTime, u.EndTime)/360 
});