public ActionResult AssignUsers(ProjectUserViewModel model)
        {
            UserProjectsHelper helper = new UserProjectsHelper();

            foreach (var user in model.SelectedUsers)
            {
                if (!helper.IsUserOnProject(user, model.Project.Id))
                {
                    helper.AddUserToProject(user, model.Project.Id);
                }
            }
            foreach (var user in db.Users.ToList())
            {
                if (!model.SelectedUsers.Contains(user.Id))
                {
                    helper.RemoveUserFromProject(user.Id, model.Project.Id);
                }
            }


            db.SaveChanges();

            return(RedirectToAction("Index", "Projects", model));
        }