單擊同一個按鈕實現顯示“全部串列埠”和“可用串列埠”想切換

#region  全部串列埠和可用串列埠切換
        private void button1_Click(object sender, EventArgs e)
        {
            switch (button1.Text)
            {
                case "可用串列埠":
                    try
                    {
                        button1.Text = "全部串列埠";
                        cb_port.Items.Clear();
                        string[] str = SerialPort.GetPortNames();
                        for (int i = 0; i < str.Length; i++)
                        {
                            cb_port.Items.Add(str[i]);
                        }
                        cb_port.SelectedIndex = 0;
                    }
                    catch (Exception)
                    {
                        MessageBox.Show("沒有可用埠","提示");
                    }
                    break;
                case "全部串列埠":
                    button1.Text = "可用串列埠";
                    cb_port.Items.Clear();
                    for (int i = 1; i <= 16; i++)
                    {
                        cb_port.Items.Add("COM"+i);
                    }
                    cb_port.SelectedIndex = 0;
                    break;
                default:
                    MessageBox.Show("請選擇可用串列埠");
                    break;
            }
        }
        #endregion