the class you refer to belongs to privacy lists which are/were in the XMPP core. Using privacy lists you can set rules to block or allow communications. Privacy lists need server side support. And there are not many existing servers which support them. Is you use the GTalk server then i don't think you can use this feature. AFAIK the GTalk server has no support for privacy lists.
What you can so is store a local list of contacts you want to block. Then check all incoming stanzas against this list.
foreach (string blockedContact in BlockedContacts)
{
if(packet.From.Bare== blockedContact)
{
// ignore this packet
return;
}
}
Alex
PS: Privacy lists will be removed from the XMPP core, because they were to complex for the most developers. The JSF is working on new extensions for communications blocking which you will find in the XEP list.