C# LINQ GROUP BY 和 MAX()
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时间：2020-08-09 12:23:55 来源:igfitidea点击:
LINQ GROUP BY and MAX()
提问by Remo H. Jansen
I'm trying to find out how to write an SQL sentence in LINQ but I can't find a way to do it for the moment, this is the SQL command:
我试图找出如何在 LINQ 中编写 SQL 语句，但我暂时找不到方法，这是 SQL 命令：
SELECT cs.Site_Name, MAX(ed.EffectiveDate_Date)
FROM [WAPMaster].[Factsheets].[EffectiveDate] ed,
[WAPMaster].[Configuration].[Site] cs
WHERE cs.Site_Id = ed.EffectiveDate_SiteId
GROUP BY cs.Site_Name
Can someone help me witht he linq syntax please?
有人可以帮我使用 linq 语法吗？
**I'm trying this so far (thanks levanlevi)
**到目前为止我正在尝试这个（感谢levanlevi）
var test = (from e in this._wapDatabase.EffectiveDates
join c in this._wapDatabase.Sites
on c.Site_Id equals e.EffectiveDate_SiteId
group e by c.Site_Name into r
select new
{
r.Key.SiteName,
EffectiveDate = r.Max(d => d.EffectiveDate_Date)
});
But I'm getting the following error:
但我收到以下错误：
采纳答案by levi
SELECT cs.Site_Name ,
MAX(ed.EffectiveDate_Date)
FROM [WAPMaster].[Factsheets].[EffectiveDate] ed ,
[WAPMaster].[Configuration].[Site] cs
WHERE cs.Site_Id = ed.EffectiveDate_SiteId
GROUP BY cs.Site_Name
from e in WAPMaster.Factsheets.EffectiveDate
join c in WAPMaster.Configuration.Site
on c.Site_Id equals e.EffectiveDate_SiteId
group e by c.Site_Name into r
select new { SiteName = r.Key, EffectiveDate = r.Max(d=>d.EffectiveDate_Date)}
回答by userGS
var test = (from effectiveDates in this._wapDatabase.EffectiveDates
from sites in this._wapDatabase.Sites
where sites.Site_Id = effectiveDates.EffectiveDate_SiteId
group effectiveDates by sites.Site_Id into g
select new { siteId = g.key , effectiveDate = g.max(ed => ed.EffectiveDate_Date)});
