I have model whith 3 tabels and one is link table with additional field:
Groups
Id
Name

Users
Id
Name

Roles
Id
Name

LinkTable
Id
GroupId
UserId
RoleId

The quuestion is how to add 3 related entities:
Code bellow doesn't work.

using (var db = new dbEntities())  
        {  
            db.Groups.AddObject(Group.CreateGroup(1, "TestGroup"));  
            db.Users.AddObject(User.CreateUser(1, "AdminUser"));  
            db.Roles.AddObject(Role.CreateRole(1, "Admin"));  
            db.UserGroupRoles.AddObject(UserGroupRole.CreateUserGroupRole(1, 1, 1, 1));  
            db.SaveChanges();  
        }