private void CardListbox_MouseDoubleClick(object sender, MouseButtonEventArgs e)
{
ListBoxItem item = ItemsControl.ContainerFromElement(sender as ListBox, e.OriginalSource as DependencyObject) as ListBoxItem;
if (item != null)
{
ExprElement element = item.DataContext as ExprElement;
InputTextBox.Text = element.PrevInput;
InputTextBox.CaretIndex = element.PrevInput.Length;
InputTextBox.ScrollToEnd();
}
}