[英]Entity Framework Query for inner join
什么是查询:
select s.* from Service s
inner join ServiceAssignment sa on sa.ServiceId = s.Id
where sa.LocationId = 1
在实体框架中?
这就是我写的:
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();
但这是错的。 有人可以指导我走这条路吗?
from s in db.Services
join sa in db.ServiceAssignments on s.Id equals sa.ServiceId
where sa.LocationId == 1
select s
db
是你的DbContext
。 生成的查询看起来像(EF6的示例):
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
如果有人对Method语法感兴趣,如果你有一个导航属性,那很容易:
db.Services.Where(s=>s.ServiceAssignment.LocationId == 1);
如果你不这样做,除非有一些我不知道的Join()
覆盖,我认为它看起来很粗糙(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);
如果可用,您可以使用导航属性。 它在SQL中生成内部联接。
from s in db.Services
where s.ServiceAssignment.LocationId == 1
select s
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