C# 内部联接的实体框架查询
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Entity Framework Query for inner join
提问by TheWebs
What would be the query for:
什么是查询：
select s.* from Service s
inner join ServiceAssignment sa on sa.ServiceId = s.Id
where sa.LocationId = 1
in entity framework?
在实体框架中？
This is what I wrote:
这是我写的：
var serv = (from s in db.Services
join sl in Location on s.id equals sl.id
where sl.id = s.id
select s).ToList();
but it's wrong. Can some one guide me to the path?
但这是错误的。有人可以指导我走这条路吗？
采纳答案by Sergey Berezovskiy
from s in db.Services
join sa in db.ServiceAssignments on s.Id equals sa.ServiceId
where sa.LocationId == 1
select s
Where dbis your DbContext. Generated query will look like (sample for EF6):
哪里db是你的DbContext。生成的查询将如下所示（EF6 示例）：
SELECT [Extent1].[Id] AS [Id]
-- other fields from Services table
FROM [dbo].[Services] AS [Extent1]
INNER JOIN [dbo].[ServiceAssignments] AS [Extent2]
ON [Extent1].[Id] = [Extent2].[ServiceId]
WHERE [Extent2].[LocationId] = 1
回答by The Lonely Coder
You could use a navigation property if its available. It produces an inner join in the SQL.
如果可用，您可以使用导航属性。它在 SQL 中产生一个内部联接。
from s in db.Services
where s.ServiceAssignment.LocationId == 1
select s
回答by Michael Blackburn
In case anyone's interested in the Method syntax, if you have a navigation property, it's way easy:
如果有人对 Method 语法感兴趣，如果您有导航属性，那就很简单了：
db.Services.Where(s=>s.ServiceAssignment.LocationId == 1);
If you don't, unless there's some Join()override I'm unaware of, I think it looks pretty gnarly (and I'm a Method syntax purist):
如果你不这样做，除非有一些Join()我不知道的覆盖，我认为它看起来很粗糙（而且我是一个方法语法纯粹主义者）：
db.Services.Join(db.ServiceAssignments,
s => s.Id,
sa => sa.ServiceId,
(s, sa) => new {service = s, asgnmt = sa})
.Where(ssa => ssa.asgnmt.LocationId == 1)
.Select(ssa => ssa.service);
