LINQ语句不编译

Question

该语句不会编译:

query = from g in context.GridViews 
   join f in context.GridViewFavorites on g.ID equals f.GridViewID into gf
   where g.GridTypeID == id && ( g.IsShared == true || g.RepID == me.clsRep.OID) 
   && f.RepID == me.clsRep.OID
   select g;

编译器错误是这样的(并且它强调了where子句的最后一部分:

当前上下文中不存在名称"f"

它的逻辑SQL对应物是:

declare @RepID int
declare @GridTypeID int
select @RepID=15, @GridTypeID=5

select g.*,f.*
from
   GridViews g
   left outer join GridViewFavorites f on f.GridViewID = g.ID
where
   g.GridTypeID = @GridTypeID and (g.IsShared = 1 or g.RepID == @RepID) 
   and f.RepID == @RepID

注意:根据@hdv的好处,SQL样本实际应该是:

select g.*,f.*
from
   GridView g
   left outer join GridViewFavorite f on f.GridViewID = g.ID and f.RepID = @RepID
where
   g.GridTypeID = @GridTypeID and (g.IsShared = 1 or g.RepID = @RepID) 

Answer 1

它是你加入的"进入"部分 - 一旦你加入"组",连接变量(f在这种情况下)超出了范围 - 你必须使用它gf.或者,鉴于您根本没有在查询中使用 gf,也许您应该into gf完全摆脱该部分,这是一个普通的连接而不是组连接.

但是,这不会给你一个左外连接.如果您想要左外连接,您可能需要:

query = from g in context.GridViews 
   join f in context.GridViewFavorites on g.ID equals f.GridViewID into gf
   from f2 in gf.DefaultIfEmpty()
   where g.GridTypeID == id && (g.IsShared == true || g.RepID == me.clsRep.OID) 
   && (f2 == null || f2.RepID == me.clsRep.OID)
   select g;