C# 方法返回未知长度数组

#region 获取根菜单ID
        private string[] GetRootMenuID(string userName)
        {
            SPList userBlockList = web.Lists[SysConst.T_UserBlock];
            var qList = (from SPListItem userblock in userBlockList.Items where userblock.GetStringValue("UserAD").Equals(userName) select new { MenuID = userblock.GetStringValue("RootMenuID") }).Distinct();

            System.Collections.ArrayList list = new System.Collections.ArrayList();
            if (qList != null)
            {
                foreach (var q in qList)
                {
                    list.Add(q.MenuID);
                }
            }
 
            return (string[])list.ToArray(typeof(string));
        }
        #endregion