求助， switch case 匹配字符串

求助， switch case 匹配字符串
在网上看到这样一个实例，switch case 居然可以匹配字符串，为什么我尝试了好久还出错，switch case无法匹配字符串，


当多个RadioButton同在一个容器里面的时候，多半的操作都是要得到其中一个的值这个时候我们就没有必要去为每一个RadioButton写一个CheckedChange事件，这样会写很多代码，太累了。这个时候我们就可以借住委托来添加一个新的事件，用新的事件代替所有RadioButton的CheckedChange事件。我要实现的要求就是：当选择中任意一个RadioButton的时候Label17就变成我选择的RadioButton的Text值      




  public void radioBtn_CheckedChange(object sender, EventArgs e)
        {
            if (!((RadioButton)sender).Checked)
            {
                return;
            }
            string rechargeMoney = string.Empty;
            switch (((RadioButton)sender).Text.ToString())
            {
                case "10":
                    rechargeMoney = "10";
                    this.lbl_money_tip.Text = rechargeMoney;
                    break;
                case "20":
                    rechargeMoney = "20";
                    this.lbl_money_tip.Text = rechargeMoney;
                    break;
                case "30":
                    rechargeMoney = "30";
                    this.lbl_money_tip.Text = rechargeMoney;
                    break;
                case "40":
                    rechargeMoney = "40";
                    this.lbl_money_tip.Text = rechargeMoney;
                    break;
                case "50":
                    rechargeMoney = "50";
                    this.lbl_money_tip.Text = rechargeMoney;
                    break;
                case "100":
                    rechargeMoney = "100";
                    this.lbl_money_tip.Text = rechargeMoney;
                    break;
                default:
                    break;
            }
        }


错误现象：