Question

In my database, I have a user table and a workgroup table, and a many-to-many relationship. A user can belong to one or more workgroups. I am using entity framework for my ORM (EF 4.1 Code First).

User Table has users:

1,2,3,4,5,6,7,8,9,10

Workgroup table has workgroups:

A,B,C, D

WorkgroupUser table has entries

A1, A2, A3, A4, A5
B1, B3, B5, B7, B9
C2, C4, C6, C8, C10
D1, D2, D3, D9, D10

What I would like to do is:
Given user 4, it belongs to workgroups A,C
and has common users

1,2,3,4,5 (from workgroup A) and 
2,4,6,8,10 from workgroup C

and the distinct set of users in common is 1,2,3,4,5,6,8,10

How do I write a LINQ statement (preferably in fluent API) for this?

Thank you,

Answer 1

Here’s the general idea (since I don’t know the properties of User and WorkGroup entity)

var result = context.users.Where(u => u.ID == 4)
                          .SelectMany(u => u.WorkGroups.SelectMany(wg => wg.Users))
                          .Distinct()