private void DataSource_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
        {
            switch (e.Action)
            {
            case NotifyCollectionChangedAction.Add:
                foreach (Users item in e.NewItems)
                {
                    BL_Users.Save(item);
                }
                break;

            case NotifyCollectionChangedAction.Remove:
                foreach (Users item in e.OldItems)
                {
                    BL_Users.Delete(item);
                }
                break;
            }
        }