C# 如何使用 Linq“不在”
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/15424770/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
how to use Linq " NOT IN"
提问by user1348351
I'm using Entity Framework
So I want to write a sql command using two tables - tblContractor and tbSiteByCont tables.
It looks like this in SQL
我正在使用实体框架
所以我想使用两个表编写一个 sql 命令 - tblContractor 和 tbSiteByCont 表。在 SQL 中看起来像这样
SELECT PKConID, Fname, Lname
FROM tblContractor
WHERE (PKConID NOT IN
(SELECT FKConID
FROM tbSiteByCont
WHERE (FKSiteID = 13)))
but I don't know how to write in Linq.
但我不知道如何在 Linq 中写作。
I tried like this
我试过这样
var query1 = from s in db.tblSiteByConts
where s.FKSiteID == id
select s.FKConID;
var query = from c in db.tblContractors
where c.PKConID != query1.Any()
select Contractor;
But this doesn't work. So how should I write it? What is the procedure? I'm new to Linq.
但这不起作用。那我应该怎么写呢？程序是什么？我是 Linq 的新手。
采纳答案by John Woo
var _result = from a in tblContractor
where !(from b in tbSiteByCont
where FKSiteID == 13
select b.FKConID)
.Contains(a.PKConID)
select a;
or
或者
var siteLst = tbSiteByCont.Where(y => y.FKSiteID == 13)
.Select(x => x.FKConID);
var _result = tblContractor.Where(x => !siteLst.Contains(x.PKConID));
回答by John Andrade
I'd use a HashSet, it ensures you only evaluate the sequence once.
我会使用 HashSet，它确保您只对序列进行一次评估。
var result = from p in tblContractor
let hasht = new HashSet<int>((from b in tbSiteByCont
where b.FKSiteID == 13
select b.PKConID).Distinct())
where !hasht.Contains(p.PKConID)
select p;
回答by BeSome
may this work too
这也可以工作
var _result = from a in tblContractor
.Where(c => tbSiteByCont
.Count(sbc => sbc.FKSiteID == 13 && c.PKConID == sbc.FKConID) == 0)
