WebControl - Declarative List

I would like to create the following control to do the following:


<asp:SomeControl id="someCustomWebControl" runat="server">
      <add key="Data1" Value="Test String" />
      <add key="Data2" Value="Another Test String"/>
      <add key="Data3" Value="Another String" />
</asp:SomeControl>


The code I have so far is:
[ParseChildren(true, "Data")]
    public class CustomWebControl: WebControl
    {
        [PersistenceMode(PersistenceMode.InnerDefaultProperty)]
        public NameValueCollection Data
        {
         &nb ...