<tc:NamingPanel runat="server" ID="ParentPanel" ClientIDMode="Static"> 
  <tc:NamingPanel runat="server" ID="NamingPanel1" ClientIDMode="Predictable"> 
    <asp:TextBox ID="TextBox1" runat="server" Text="Hello!"></asp:TextBox> 
  </tc:NamingPanel> 

</tc:NamingPanel>