Linq 中的简单左连接无法按预期工作

Question

我想将以下查询转换为 Linq

select m.Id,m.MenuName,mr.CanAdd,mr.CanDelete,mr.CanEdit
from Menu m
left join MenuRole mr on m.Id=mr.MenuID
and mr.DesignationID=1 where m.ParentID<>0

预期结果是

我尝试了以下但没有得到想要的结果

var test = (from m in _db.Menus
                   join mr in _db.MenuRoles on m.Id equals mr.MenuID  into t
                   from rt in t.Where(x=>x.Menu.ParentID!=0).DefaultIfEmpty()
                   where rt.DesignationID==1
                   orderby m.Id 
                   select new MenuVM
                   {
                       CanAdd=rt.CanAdd==null?false:true,
                       CanEdit=rt.CanEdit==null?false:true,
                       CanDelete=rt.CanDelete==null?false:true,
                       MenuId=rt.Menu.Id,
                       MenuName=rt.Menu.MenuName                       
                   });

问题是Employee data没有上市

Answer 1

我认为这应该是：

from m in _db.Menus
join mr in _db.MenuRoles on m.Id equals mr.MenuID  into t
from rt in t.Where(x=>x.DesignationID==1).DefaultIfEmpty()
where m.ParentID!=0

DesignationID 转到 left join 条件，ParetID 转到 where 子句。

Select 来自 m:

select new MenuVM
{
     CanAdd=rt.CanAdd==null?false:true,
     CanEdit=rt.CanEdit==null?false:true,
     CanDelete=rt.CanDelete==null?false:true,
     MenuId=m.Id,
     MenuName=m.MenuName                       
});

Linq 中的简单左连接无法按预期工作

Simple Left join in Linq not working as expected

c#

linq

left-join