private void BtnCheckIn_Click(object sender, EventArgs e) { List <Book> memberBooks = LibraryHelper.GetMemberBooks(); if (memberBooks != null) { var selectedItems = lstCheckedOut.SelectedItems; List <Book> selectedBooks = GetSelectedItems( selectedItems); if (LibraryHelper.CheckInBooks(selectedBooks)) { MessageBox.Show("Check-In Successful."); LoadBoxes(); } else { MessageBox.Show("Nothing selected."); } } else { MessageBox.Show("Nothing to check-in."); } }