Question

我有一个用户表和一个组表，一个用户可以成为许多组的一部分

[USERID]----*-[USERID GROUPID]-*-----[GROUPID]
                (join table)

public partial class user
{
    public int user_id { get; set; }
    public string name { get; set; }
    public virtual ICollection<group> groups{ get; set; }
}

public partial class group
{
    public int user_id { get; set; }
    public string name { get; set; }
    public virtual ICollection<user> users{ get; set; }
}

1）我需要返回属于特定组的所有用户

var queryable = (from g in db.groups
                  where g.group_id == id
                  select g.users)
                  .ToList()
                  .Select(u => new {    
                      id = u.id,      //Error does not contain definition for id
                      name = u.name   //Error does not contain definition for name
                   });

2）我需要返回属于特定组的特定用户

感谢您的建议

Answer 1

我需要返回属于特定组的所有用户

Lambda语法：

db.groups.Where(g => g.group_id == id).SelectMany(g => g.users)

或查询语法：

from g in db.groups
where g.group_id == id
from u in g.users
select u

我需要返回属于特定群组的特定用户

就像上面的查询一样，还有一个额外的过滤器

db.groups.Where(g => g.group_id == id)
         .SelectMany(g => g.users)
         .Where(u => u.id == userId)

查询语法：

from g in db.groups
where g.group_id == id
from u in g.users
where u.id == userId
select u

Answer 2

尝试这样的事情：

var queryable = (from p in db.plants
             join u in db.users on p.userId equals u.id
              where p.plant_id == plant_id
              select u)
              .ToList()
              .Select(u => new {    
                  id = u.id,      
                  name = u.name   
               });

其中p.userId是连接工厂和用户表的列

Answer 3

var queryable = (from p in db.plants
                join u in db.users on p.userId equals u.id
                where p.plant_id == plant_id
                select new { p.id, p.name, u.name}).ToList();

Linq查询连接表

3 个答案: