使用Entity Framework返回2个表中的数据 [英] Return data from 2 tables with Entity Framework

问题描述

我正在使用MVC3和Entity Framework，但是到了需要从不同表中获取更多数据的地步.通常我会做这样的事情来从表中获取数据:

I'm working with MVC3 and Entity Framework but i came to a point where i need more data from different tables. Usually i'd do something like this to get data from a table:

Table: Users
id
username

在代码中，我将执行以下操作以获取所有用户:

In code i would do something like this to get all the users:

public static IEnumerable<Users> GetUsers( int userId )
{
    MyEntities ent = new MyEntities();

    return from g in ent.Users
           where g.OwnerUserId == userId
           select g;
}

所以这会让我所有的用户回来.

So this would give me all my users back.

但是用户可以加入一个组，而我必须从特定组中获取所有用户名.

But a user can join a group, and i have to get all the usernames from a specific group.

Table: userGroups
id
fk_user_id
fk_group_id

现在，如果我要使用此代码:

Now if i'd use this code:

public static IEnumerable<userGroups> GetUsersFromGroup( int groupId )
{
    MyEntities ent = new MyEntities();

    return from g in ent.userGroups
           where g.OwnerUserId == userId
           select g;
}

现在显然，这仅返回"userGroups"表中的数据.但是不知何故我也需要用户表中的用户名.我如何也可以获取这些数据，并且仍然以IEnumerable的形式返回我的"userGroups"?

Now obviously this only returns me the data from the "userGroups" table. But somehow i also need the username from the Users table. How can i get that data too and still return my "userGroups" as an IEnumerable?

在SQL中，我只是做一个LEFT JOIN，但是我真的不知道在这里是如何工作的.

In SQL i'd simply do a LEFT JOIN, but i can't really figure out how that works here.

推荐答案

类似这样的事情:

var query = from g in ent.userGroups
            join u in ent.Users on g.fk_user_id equals u.userID
            select new { g, u, });

或使用 LEFT JOIN

var query = (from g in ent.userGroups
             from u in ent.Users.Where(a => a.fk_user_id == u.userID).DefaultIfEmpty()
             select new { g, u, });

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