public partial class _Default : System.Web.UI.Page
{

 if (!IsPostBack)
        {
            string conn_string = "Integrated Security=SSPI;Persist Security Info=False;Data Source=WY;database=GHRQ";
            string Query = "select id,funcname,funcparentid from treeview order by ID";
            using (SqlConnection connection = new SqlConnection(conn_string))
            {
                SqlCommand command = new SqlCommand();
                command.Connection = connection;
                command.CommandType = CommandType.Text;
                command.CommandText = Query;
                SqlDataAdapter Adapter = new SqlDataAdapter();
                Adapter.SelectCommand = command;
                DataTable dataTable = new DataTable();
                Adapter.Fill(dataTable);
                BindTreeView(dataTable, TreeView1.Nodes, "0");
            }
        }
    }

    private void BindTreeView(DataTable dataTable, TreeNodeCollection TreeNodes, string parentId)
    {
        DataView dataView = new DataView(dataTable);
        TreeNode node;
        dataView.RowFilter = "funcparentid=" + "'" + parentId + "'";
        foreach (DataRowView dataRowView in dataView)
        {
            node = new TreeNode();
            node.Text = dataRowView["funcname"].ToString();

            TreeNodes.Add(node);
            BindTreeView(dataTable, node.ChildNodes, dataRowView["ID"].ToString());
        }
    }

}