This AJAX enabled control implements a Lookup Server Control that helps entering a country name. Instead of downloading the complete list of countries a WebService is used to support the autocomplete functionality.
The AJAX control is using a webservice for retrieving the list of sub-nodes (folders and files) from a given node (the user clicks):
public string GetPrefixedEntries(string prefix)
To support other datasets for the lookup you just need to implement another webservice with the same method.
On the web page a AJAX enabled web control is included:
<ajax:Lookup ID="Lookup1" lookupservice="CountryLookup" runat="server" />
You can find a more detailed documentation in the accompanying book at: http://www.mathertel.de/Ajax/AJAXeBook.aspx
This page is part of the http://www.mathertel.de/ web site.