将SQL Select转换为实体框架跨五个表的联接

问题描述

我开始在新项目中使用Entity Framework，以查看其是否有效.

I start to use Entity Framework in a new project, to see if it is valid or no.

但是我陷入了需要加入5张桌子的部分.我很确定他们之间的关系还可以，我可以选择使用 .include(x => x.table)的三个(因为我在互联网上找到了)，而且我知道将需要使用 Join()，但我不知道如何.

But I got stuck in a part where I need to join 5 tables. I am pretty sure that the relationship between them are ok, I can select using .Include(x => x.table) for only three (because I found on the internet), and I know I will need to Use Join(), but I don't know how.

SQL中的选择是:

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

推荐答案

对实体使用LINQ，并假定DbSet上下文属性名称与表名称相同，这是使用C#表达式的查询:

Using LINQ to Entities and assuming DbSet context property names are same as table names, here is the query using C# expression:

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

如果要使用具有lambda表达式样式的 Join 方法，以下是多种联接语法(使用LINQPad从上面的语法转换):

If you want to use Join method with lambda expression style, here is multiple join syntax (converted from above syntax with LINQPad):

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.

这篇关于将SQL Select转换为实体框架跨五个表的联接的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！