C#主窗体获取用户控件返回值并赋值给主窗体失败

//主窗体       private List<string> _recordlist;        public List<string> RecordList = new List<string>() ;        /// <summary>        /// 已选择的RecordID List        /// </summary>        public List<string> RecordList        {            get            {                _recordlist = new List<string>();                return _recordlist;            }            set            {                _recordlist = value;            }        }//主窗体构造函数      public FrmDownLoadBaleScheme(List<string> ListID, bool type): this()        {            this.RecordList = ListID;//这里一直赋值不成功，ListID显示有值，但RecordList一直没有值        }         //用户控件窗体        //单个点击选中，返回值给主窗体        private void pnl_packinglist_Click(object sender, EventArgs e)        {                RECORD_ID_LIST.Add(lbl_record_id.Text);                FrmDownLoadBaleScheme form = new FrmDownLoadBaleScheme(RECORD_ID_LIST, true);         }