public static IList<string> strlist = null; public IList<string> setArray(string str){       strlist.Add(str);       return strlist;}public IList<string> getArray(){            IList<string> rtn = strlist;            strlist.Clear();            return rtn;} private void button1_Click(object sender, EventArgs e){          setArray("a");} 我想問一下為什么strlist.Add(str);的時(shí)候會(huì)報(bào)錯(cuò)，不能存字符串到里面去嗎？