asp.net使用dorpdownlist绑定无限级分类

      　/// <summary>
        /// 绑定父项分类
        /// </summary>　　　　　　　　 
　　　　 protected void DDLBindClass()
        {
            DataSet ds = new BLL_Cpgl_cpfl().GetAllList();
            DataTable dt = ds.Tables[0];
            DataRow[] dr = dt.Select("Parentid=0");
            for (int i = 0; i < dr.Length; i++)
            {
                ddlParent.Items.Add(new ListItem(dr[i]["name"].ToString(), dr[i]["id"].ToString()));
                BindChild(dt, dr[i]["id"].ToString(), 1);
            }
            this.ddlParent.Items.Insert(0, new ListItem("--请选择--", "0"));
        }       
　　　　 /// <summary>       
　　　　 /// 绑定子分类信息
        /// </summary>
        /// <param name="dt">数据表</param>
        /// <param name="parentID">父分类ID </param>
        /// <param name="count">分级级别</param>
        private void BindChild(DataTable dt, string parentID, int count)
        {
            DataRow[] dr = dt.Select("Parentid= '" + parentID + "'");
            string strindex = "--";
            for (int k = 0; k < count; k++)
            {
                strindex = System.Web.HttpUtility.HtmlDecode("&nbsp;") + System.Web.HttpUtility.HtmlDecode(" ") + strindex;
            }
            for (int i = 0; i < dr.Length; i++)
            {
                ddlParent.Items.Add(new ListItem(strindex + dr[i]["name"].ToString(), dr[i]["id"].ToString()));
                BindChild(dt, dr[i]["id"].ToString(), count + 1);
            }

        }