初学者求一Linq表达式
日期：2014-05-20 浏览次数：20876 次
菜鸟求一Linq表达式
下面的SQL 改成用 Linq 实现。
SELECT
c.id,
c.CustomersName as name,
f.FollowUpTheWay as names,
f.NextFollowDate,
f.FollowDate,
f.id as fid
from dbo.Slgl_CustomerReception as c
left join dbo.Slgl_FollowUpRecords as f on
f.id = (select TOP(1) id from dbo.Slgl_FollowUpRecords where CustomersId = c.id and FollowDate <= '2011-7-20' order by id DESC)
where c.ProjectId = 9
简要写下就可以了 主要小括号里面的内容 不知道怎么转
------解决方案--------------------
下面的SQL 改成用 Linq 实现。
SELECT
c.id,
c.CustomersName as name,
f.FollowUpTheWay as names,
f.NextFollowDate,
f.FollowDate,
f.id as fid
from dbo.Slgl_CustomerReception as c
left join dbo.Slgl_FollowUpRecords as f on
f.id = (select TOP(1) id from dbo.Slgl_FollowUpRecords where CustomersId = c.id and FollowDate <= '2011-7-20' order by id DESC)
where c.ProjectId = 9
简要写下就可以了 主要小括号里面的内容 不知道怎么转
------解决方案--------------------
- C# code
var query=from c in Slgl_CustomerReception
where c.ProjectId==9
let id=Slgl_FollowUpRecords.Where(r=>r.CustomerId==c.id
&& r.FollowDate<=Convert.ToDateTime("2011-7-20"))
.OrderByDescending(r=>r.id).First().id
join f in Slgl_FollowUpRecords
on f.id equals id into g
from f in g.DefaultIfEmpty()
select new
{
id=c.id,
name=c.CustomersName,
names=f==null?"":f.FollowUpTheWay,
FollowDate=f==null?DateTime.Now:f.FollowDate,
fid=f==null?0:f.id
};
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