递归一个List，可自己根据需要改造为通用型。

        /// <summary>
        /// 递归一个list<provinceorg>
        /// </summary>
        /// <returns></returns>
        public void recursionprovinceorgs(list<provinceorg> provinceorgs, ref list<provinceorg> _provinceorgs)
        {
            if (provinceorgs != null && provinceorgs.count() > 0)
            {
                // 1、通过linq查询出children为空的。
                var _provinceorgs_ = provinceorgs.where(p => p.children.count() == 0);
                if (_provinceorgs_.count() > 0)
                {
                    //2、将children为空的添加至_provinceorgs
                    _provinceorgs.addrange(_provinceorgs_);
                }

                // 处理剩余不为空的,父级的org
                var _provinceorgs_surplus = provinceorgs.where(p => p.children.count() > 0);
                foreach (provinceorg provinceorg in _provinceorgs_surplus)
                {
                    provinceorg provinceorgclone = provinceorg.clone();
                    _provinceorgs.add(provinceorgclone);
                    recursionprovinceorgs(provinceorg.children, ref _provinceorgs);
                }
            }
        }

　实体类：

    public class provinceorg : icloneable
    {
        public int orgid { get; set; }
        public int parentorgid { get; set; }
        public int areaid { get; set; }
        public string areacode { get; set; }
        public string orgname { get; set; }
        public string fullorgname { get; set; }
        public string orgtype { get; set; }
        public string state { get; set; }
        public string orgcode { get; set; }
        public int seq { get; set; }
        public string isbusdep { get; set; }
        public string depcatecode { get; set; }
        public string legalperson { get; set; }
        public string contacts { get; set; }
        public string phone { get; set; }
        public string address { get; set; }
        public string orgfunctions { get; set; }
        public int num;
        public list<provinceorg> children { get; set; }

        /// <summary>
        /// 克隆并返回一个对象。
        /// </summary>
        /// <returns></returns>
        public provinceorg clone()
        {
            provinceorg p = (provinceorg)this.memberwiseclone();
            p.children = new list<provinceorg>();
            return p;
        }

        object icloneable.clone()
        {
            return this.clone();
        }
    }