public ActionResult UpdateRoles(string username, string[] roles, string text, string role, int nbPage)
{
var existing = BLLUsers.ListUserRoles(username);
var toAdd = roles.Where(c => !existing.Any(d => d.Id == c));
var toDelete = existing.Where(c => !roles.Contains(c.Id)).ToArray();
BLLUsers.AddRolesToUser(username, toAdd.ToArray());
BLLUsers.RemoveRolesToUser(username, toDelete.Select(c => c.Id).ToArray());
return(RedirectToAction("UserList", new { text = text, role = role, nbPage = nbPage }));
}