private void KeyUp(System.Windows.Input.KeyEventArgs e)
        {
            try
            {
                switch (e.Key)
                {
                case System.Windows.Input.Key.Delete:
                    string            lmsg     = "Delete the selected cartridge?";
                    string            lcaption = "Delete Cartridge Data";
                    MessageBoxButtons lbtns    = MessageBoxButtons.YesNo;
                    DialogResult      lrst     = MessageBox.Show(lmsg, lcaption, lbtns, MessageBoxIcon.Warning);
                    if (lrst == DialogResult.Yes)
                    {
                        foreach (Cartridge lc in Cartridges)
                        {
                            if (SelectedCartridge.ID == lc.ID)
                            {
                                Cartridges.Remove(lc);
                                SelectedCartridge = null;
                                break;
                            }
                        }
                    }
                    break;

                case System.Windows.Input.Key.OemPlus:
                    AddCartridge();
                    break;
                }
            }
            catch
            {
            }
        }