private void UserCommand_OnPreviewKeyUp(object sender, KeyEventArgs e)
{
if (e.Key != Key.Down || ProcessNames.Items.Count <= 0)
{
return;
}
ProcessNames.Focus();
ProcessNames.SelectedIndex = 0;
ProcessNames.UpdateLayout();
var matchedItem = (ListBoxItem)ProcessNames.ItemContainerGenerator.ContainerFromItem(ProcessNames.SelectedItem);
matchedItem.Focus();
}