public void AddUserToScheduleItem(ScheduleItemAddress scheduleItemAddress, Guid userID)
{
var scheduleItem = GetScheduleItem(scheduleItemAddress);
repository.AddUserRelationship(scheduleItem.ToScheduleItemSmall(), userID);
//cache.InvalidateItem(scheduleItem);
//var key = string.Format("GetScheduleItemsByUser-UserID:{0}", userID);
//cache.InvalidateContains(key, StringComparer.InvariantCultureIgnoreCase);
}