treeview 无限级别绑定并控制收缩层次

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.ComponentModel;

public partial class UserControl_prlist : System.Web.UI.UserControl
{
    protected void Page_Load(object sender, EventArgs e)
    {
        //if (IsPostBack)
        //{

            Hisidon.Components.DB db = new Hisidon.Components.DB();
            this.ViewState["ds"] = db.getDataSet("select * from 产品类别表 order BY 排序");
            db.Free();
            TreeView1.Nodes.Clear();
            AddTree(0, (TreeNode)null);

          //  TreeView1.CollapseAll();

           //展开2层
           // TreeNodeCollection collection = TreeView1.Nodes;
            
            
            //foreach (TreeNode node in collection)
            //{
            //     node.Expand();
            //}
            //收缩所有
            ExpandNodes(TreeView1, false);

            bindclass();
  
    }

    public void ExpandNodes(TreeView treeview, bool Expand)
    {
        foreach (TreeNode n in treeview.Nodes)
        {
            n.Expanded = Expand;
          //  ExpandNodes(n, Expand);
        }
    }
    public string isclass()
    {
        if (Repeater2.Items.Count == 0)
        {
            return "暂无类别";
        }
        return "";
    }
    void bindclass()
    {
        Hisidon.Components.DB db = new Hisidon.Components.DB();
        db.bindRepeater("SELECT [产品类别名称], [产品类别编号], [品牌图标] FROM [产品类别表] where 品牌图标 <>'' and 是否推荐 =1 ORDER BY [排序]",Repeater2);

        db.Free();
    }
    //递归添加树的节点
    public void AddTree(int ParentID, TreeNode pNode)
    {
        DataSet ds = (DataSet)this.ViewState["ds"];
        DataView dvTree = new DataView(ds.Tables[0]);

        //过滤父编号,得到当前的所有子节点
        dvTree.RowFilter = "[上级父编号] = " + ParentID;

        foreach (DataRowView Row in dvTree)
        {
            TreeNode Node = new TreeNode();
            if (pNode == null)
            {    //添加根节点
                Node.Text = Row["产品类别名称"].ToString();

                Node.NavigateUrl = "../class.aspx?classid=" + Row["产品类别编号"].ToString();

                TreeView1.Nodes.Add(Node);
                Node.Expanded = true;
                AddTree(Int32.Parse(Row["产品类别编号"].ToString()), Node);        //再次递归
            }
            else
            {   //̀添加当前节点的子节点
                Node.Text = Row["产品类别名称"].ToString();
                Node.NavigateUrl = "../class.aspx?classid=" + Row["产品类别编号"].ToString();

                pNode.ChildNodes.Add(Node);
                Node.Expanded = true;
                AddTree(Int32.Parse(Row["产品类别编号"].ToString()), Node);     //再次递归
            }
        }
    }
}