private bool checkedStatus = false;
        /// <summary>
        /// 當前按鈕選擇狀態，true已選擇
        /// </summary>
        public bool CheckedStatus
        {
            get {
                return checkedStatus;
            }
            set {
                checkedStatus = value;
            }
        }

        public VoidableRadioButton()
            : base()
        { }

        protected override void OnCheckedChanged(EventArgs e)
        {
            base.OnCheckedChanged(e);
            if (!this.Checked)
            {
                checkedStatus = false;
            }
        }

        protected override void OnClick(EventArgs e)
        {
            base.OnClick(e);
            if (checkedStatus)
            {
                this.Checked = false;
                //Checked=false觸發了CheckedChanged，所以這里應該把狀態重置為true
                checkedStatus = true;
            }
            checkedStatus = !checkedStatus;
        }