子查询中LAMBDA

Question

我越来越

这里是我的SQL Server的查询，而我试图转换成

select * from Permission Where PermissionId in(select PermissionId from RoleDetail where RoleId =1) 

这里是我最初的拉姆达子查询

from p in Permissions 
    let rde = from rd in RoleDetails 
     select rd.PermissionId 
     where p.PermissionId ==1 
     select p 

但其表现我只有一个记录附有该角色，但实际上它有5个权限请帮助。

Answer 1

也许尝试呢？而不是试图用.Contains()，只是做在两个表加入...

from p in Permissions 
join rd in RoleDetails on p.PermissionId equals rd.PermissionId 
where rd.RoleId == 1 
select p; 

Answer 2

使用Join： -

var result = from p in Permissions 
      join rd in RoleDetails.Where(x => x.RoleId == 1) 
      on p.PermissionId equals rd.PermissionId 
      select p; 

Answer 3

你做错了这样做：

from p in Permissions 
    let rde = (from rd in RoleDetails 
       where rd.RoleId ==1 
       select rd.PermissionId) 
where p.PermissionId = rde 
select p 

见LET usage HERE

Answer 4

使用连接（在其他的建议swers）是更好的，但解决您的查询，您应该过滤rde上RoleId = 1然后过滤Permissions与rde：

from p in Permissions 
    let rde = from rd in RoleDetails 
     where rd.RoleId == 1   // filter RoleId = 1 
     select rd.PermissionId 
    where rde.Contains(p.PermissionId) // rde should contain p.PermissionId 
    select p