asp.net DropDownList中内容伪树状展示

        #region "绑定区域下拉菜单"        /// <summary>        /// 绑定树形节点        /// </summary>        public void BindAreaDropDownList()        {            DataTable dt = new AreaBLL().GetData("", " Orderby ASC");            Areaddl.Items.Add(new ListItem("请选择", "0"));            if (dt != null && dt.Rows.Count > 0)            {                foreach (DataRow row in dt.Rows)                {                    if (!DBNull.Value.Equals(row["ParentID"]) && row["ParentID"].ToString() == "0")//绑定根节点                    {                        this.Areaddl.Items.Add(new ListItem(row["Name"].ToString(), row["ID"].ToString()));                        this.bindDropChildItem(this.Areaddl, dt, row["ID"].ToString(), 1);                    }                }            }        }        /// <summary>        /// 绑定子节点        /// </summary>        /// <param name="drop">下拉菜单</param>        /// <param name="arealist">查询到的数据集</param>        /// <param name="id">当前的父节点</param>        /// <param name="length">长度</param>        public void bindDropChildItem(DropDownList drop, DataTable dt, string id, int length)        {            DataRow[] rows = dt.Select("ParentID='" + id + "'", " orderby ASC");//取出id子节点进行绑定            for (int i = 0; i < rows.Length; i++)            {                this.Areaddl.Items.Add(new ListItem(SpaceLength(length) + rows[i]["Name"].ToString(), rows[i]["ID"].ToString()));                this.bindDropChildItem(drop, dt, rows[i]["ID"].ToString(), length + 1);//空白数目加1            }        }        /// <summary>        /// 子节点前面的空白数        /// </summary>        /// <param name="i"></param>        /// <returns></returns>        protected string SpaceLength(int i)        {            string space = "";            for (int j = 0; j < i; j++)            {                space += "　";//注意这里的空白是智能abc输入法状态下的v11字符；            }            return space;        }        #endregion