how to fill tree view dynamicaly

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.Data.SqlClient;
public partial class dynamictreeview : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void TreeView1_TreeNodePopulate(object sender, TreeNodeEventArgs e)
{
if (e.Node.ChildNodes.Count == 0)
{
switch (e.Node.Depth)
{
case 0:
fillcategory(e.Node);
break;
case 1:
fillsubcat(e.Node);
break;
}
}
}
public void fillcategory(TreeNode node)
{
SqlConnection con = new SqlConnection(ConfigurationManager.AppSettings["ConnectionString"]);
con.Open();
string qry = "select * from tbl_category";
SqlDataAdapter ad = new SqlDataAdapter(qry, con);
DataSet ds = new DataSet();
try
{
ad.Fill(ds);
}
catch (Exception ex)
{
}
if (ds.Tables[0].Rows.Count > 0)
{
foreach (DataRow r in ds.Tables[0].Rows)
{
TreeNode newnode = new TreeNode(r["catname"].ToString() , r["catid"].ToString());
newnode.PopulateOnDemand = true;
node.ChildNodes.Add(newnode);
}
}
}
public void fillsubcat(TreeNode node)
{
string aid = node.Value;
SqlConnection con = new SqlConnection(ConfigurationManager.AppSettings["ConnectionString"]);
con.Open();
string qry = "select subcatid,subcatname from tbl_subcategory where catid='" + aid + "'";
SqlDataAdapter ad = new SqlDataAdapter(qry, con);
DataSet ds = new DataSet();
try
{
ad.Fill(ds);
}
catch (Exception ex)
{
}
if (ds.Tables[0].Rows.Count > 0)
{
foreach (DataRow r in ds.Tables[0].Rows)
{
TreeNode newnode = new TreeNode(r["subcatname"].ToString(), r["subcatid"].ToString());
newnode.PopulateOnDemand = false;
newnode.SelectAction = TreeNodeSelectAction.None;
node.ChildNodes.Add(newnode);
}
}
}
}