treeview 绑定2层数据，如何实现导航呢？现在只能选中，怎么设置一个链接呢？


using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;
using System.Web.Configuration;public partial class admin_pros_listcategory : System.Web.UI.Page
{
    string _connstring = WebConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {                 DataTable dtBig = GetBig();
                DataTable dtSmall = GetSmall();
                foreach (DataRow row in dtBig.Rows)
                {
                    TreeNode node = new TreeNode(row["brandname"].ToString(), row["brandid"].ToString());
                    foreach (DataRow r in dtSmall.Select("brandid=" + row["brandid"]))
                    {
                        node.ChildNodes.Add(new TreeNode(r["categoryname"].ToString(), r["categoryid"].ToString()));
                    }
                    TreeView1.Nodes.Add(node);
                }
        
        }
        
           }    public DataTable GetBig()
    {
        DataTable dt = new DataTable();
        SqlConnection con=new SqlConnection(_connstring);
        SqlCommand cmd = new SqlCommand();
        cmd.Connection = con;
        cmd.CommandText = "select brandname,brandid,shunxu from brand order by shunxu desc";
        SqlDataAdapter sda = new SqlDataAdapter(cmd);
        using (sda)
        {
            sda.Fill(dt);
        }
        return dt;
    }    public DataTable GetSmall()
    {
        DataTable dt = new DataTable();
        SqlConnection con = new SqlConnection(_connstring);
        SqlCommand cmd = new SqlCommand();
        cmd.Connection = con;
        cmd.CommandText = "select categoryname,categoryid,brandid from category ";
        SqlDataAdapter sda = new SqlDataAdapter(cmd);
        using (sda)
        {
            sda.Fill(dt);
        }
        return dt;
    }