there are two tables in the database: the User table and the Score table.

User
id    name        
1    Young        25
2    Hong         24

Score
id    userId    course    score
10    1            100
11    1            90
12    2            95
13    2            85

at present, I use this linq sentence to check:

(from u in User join s in Score
on u.id equals s.userId
select MapToEntity(u,s)).ToList());

private User MapToEntity(User u, Score s){
    u.score = s;
    return u;
}

the result of the joint survey is as follows:

{
    User{
        Young,,25
        Score{
            10,1,100
        }
    },
    User{
        Young,,25
        Score{
            11,190
        }
    }
    User{
        Hong,24
        Score{
            12,295
        }
    }
    User{
        Hong,24
        Score{
            13,285
        }
    }
}

how to get such a result through Linq search:

{
    User{
        Young,,25
        Score{
            10,1,100
        }
        Score{
            11,190
        }
    },
    User{
        Hong,24
        Score{
            12,295
        }
        Score{
            13,285
        }
    }
}