如何在实体框架查询中为.Include返回的数据指定where子句？

Question

给出以下数据库表层次结构：

Region
------
RegionId
RegionName

Country
-------
CountryId
RegionId
CountryName

Destination
-----------
DestinationId
CountryId
DestinationName

Venue
-----
VenueId
DestinationId
VenueName

我有以下实体框架查询：

var result = from region in context.Region.Include("Country.Destination.Venue") 
select region

将返回所有表中的所有行（外部联接）

是否可以引入where子句，以便只包含场地不为null的行（或使用内部联接）？

由于

Answer 1

试试这个。它应该返回您要查找的结果：只有具有相应位置的区域。

    var result = from region in context.Region.Include(Country.Destination.Venue)
                 let v = (from ctry in region.Country
                         join dest in context.Destination
                         on ctry.CountryId
                         equals dest.CountryId
                         into destGroup
                         from dests in destGroup
                         join ven in context.Venue
                         on dests.DestinationId
                         equals ven.DestinationId
                         into venGroup
                         select ctry).Any()
                 where v == true
                 select region;