1,<iewc:TreeView id=TreeView1 style="Z-INDEX: 101; LEFT: 152px; POSITION: absolute; TOP: 168px" TreeNodeSrc="categories.aspx" runat="server">
2,categories.aspx.cs

private void Page_Load(object sender, System.EventArgs e)
{
string sql=@"select categoryname as Text,'products.aspx?catid='+ltrim(str(categoryid)) as TreeNodesrc
from categories as TreeNode for xml auto ,xmlData " ;
SqlConnection sqlConn=new SqlConnection("Server=dbm-1;Uid=sa;pwd=;DataBase=Northwind");
SqlCommand com=new SqlCommand (sql,sqlConn);
DataSet ds=new DataSet();
sqlConn .Open();
ds.ReadXml(com.ExecuteXmlReader(),XmlReadMode.Fragment );
sqlConn.Close();
sqlConn=null;

ds.DataSetName ="TREENODES";
ds.WriteXml(Response.OutputStream );

}