Question

Say I have the following database:

Users
-------
UserId (PK)
UserName

Roles
-----
RoleId (PK)
RoleName

UserRoles
---------
UserId (PK)
RoleId (PK)

Users 1-M UserRoles M-1 Roles

Using LinqToSQL, I want to return the following set:

[User1], [Role1, Role2, Role3]
[User2], [Role2, Role3]
[User3], []

Etc…

What is the most efficient way to create this LinqToSql Query?

In addition, if I want to create a filter to return only users that have Role1, what would that entail?

Thx.

Answer 1

Define “efficient”. But otherwise…

from u in dataContext.Users
select new { User = u, Roles = u.UserRoles.Select(ur => ur.Role) }

And filtering users by RoleID:

from u in dataContext.Users
where u.UserRoles.Any(ur => ur.RoleID == 1)
select u

Or by some other Role attribute, say, Name:

from u in dataContext.Users
where u.UserRoles.Any(ur => ur.Role.Name == "Role 1")
select u

Combining it all together:

from u in dataContext.Users
select new
{
     User = u,
     Roles = from ur in u.UserRoles
             where ur.RoleID == 1 || ur.Role.Name == "Role 1"
             select ur.Role
}