Question

我开始在新项目中使用Entity Framework，看看它是否有效。

但是我陷入了需要加入5个表的部分。我很确定它们之间的关系没问题，我可以选择仅使用.Include(x => x.table)三个（因为我在网上找到），而且我知道我需要使用Join()，但我不知道＃39;不知道如何。

SQL中的select是：

SELECT       
    Module.*
FROM            
    UserGroup as ug 
INNER JOIN
    Group as g ON ug.IdGroup = g.IdGroup 
INNER JOIN
    GroupFunctionality as gf ON g.IdGroup = gf.IdGroup 
INNER JOIN
    Functionality as f ON gf.IdFunctionality = f.IdFunctionality 
INNER JOIN
    Screen as s ON f.IdScreen = s.IdScreen 
INNER JOIN
    Module as m ON s.IdModule = m.IdModule
WHERE
    ug.IdUser = 1

Answer 1

使用LINQ to Entities并假设DbSet上下文属性名称与表名相同，这是使用C＃表达式的查询：

from ug in db.UserGroup
join g in db.Group on ug.IdGroup equals g.IdGroup
join gf in db.GroupFuncionality on g.IdGroup equals gf.IdGroup
join f in db.Funcionality on gf.IdFuncionality equals f.IdFuncionality
join s in db.Screen on f.IdScreen equals s.IdScreen
join m in db.Module on s.IdModule equals m.IdModule
where ug.IdUser == 1
select m

如果你想使用lambda表达式样式的Join方法，这里有多个连接语法（用LINQPad从上面的语法转换）：

db.UserGroup.Join(db.Group, ug => ug.IdGroup, g => g.IdGroup, (ug, g) => new { ug = ug, g = g })
            .Join(db.GroupFuncionality, temp0 => temp0.g.IdGroup, gf => gf.IdGroup, (temp0, gf) => new {temp0 = temp0, gf = gf})
            .Join(db.Funcionality, temp1 => temp1.gf.IdFuncionality, f => f.IdFuncionality, (temp1, f) => new {temp1 = temp1, f = f})
            .Join(db.Screen, temp2 => temp2.f.IdScreen, s => s.IdScreen, (temp2, s) => new {temp2 = temp2, s = s})
            .Join(db.Module, temp3 => temp3.s.IdModule, m => m.IdModule, (temp3, m) => new {temp3 = temp3, m = m})
            .Where(temp4 => temp4.temp3.temp2.temp1.temp0.ug.IdUser == 1)
            .Select(temp4 => temp4.m)

CMIIW。

将SQL选择转换为实体框架跨五个表进行连接

1 个答案: