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(); }