Linq to Entities EF4

Question

I have a Groups domain model with name , desc and collection of users (belonging to the group)

I am trying to get all groups that a particular user belongs to. This is my LinQ statement:

var results = from p in AuthorizationService.UnitOfWork.Groups.FindAll()
                          where
                              (p.Users != null && p.Users.Select(u => u.Id).Contains(CurrentUser.Id))
                          select p.Name;

I get the following error when i try to execute the query

Cannot compare elements of type 'System.Collections.Generic.ICollection`1'. Only primitive types (such as Int32, String, and Guid) and entity types are supported.

Any help is appreciated.Thanks!

Answer 1

Remove the null testing for Users object, anyway it's lazy loaded, is your Users virtual? if it is, it is lazy-loaded, it's ok to remove the null testing then

var results = 
from p in AuthorizationService.UnitOfWork.Groups.FindAll() 
where 
     p.Users.Any(u => u.Id == CurrentUser.Id)
select p.Name;

Answer 2

Can't you go the opposite way?

var results = AuthorizationService.UnitOfWork.Users.Include("Groups").First(u => u.ID == CurrentUser.Id).Select(u => u.Groups);

Hope this helps.