检测选中的权限并输出文本，但只要出现未选的权限就会输出“无”。有什么办法能仅仅在所有权限都未选的情况下输出“无”？

  private void button1_Click(object sender, EventArgs e)
        {
            string strpop = "您选择的权限如下";
            foreach(Control ctrl in this.Controls)
            {
                if(ctrl.GetType().Name=="CheckBox")
                {
                    CheckBox cBox=(CheckBox)ctrl;
                    if(cBox.Checked==true)
                    {
                        strpop+="\n"+cBox.Text;
                    }
                    else
                    {
                        strpop = "无";
                    }
                }
            }