Google-Talk invisibility

I was trying to create an XMPP开发者_StackOverflow and a Jabber chat-program.

I was unable to set chat state to 'Invisible'. I would love to hear from users experience if this is possible and how they do that.

I don't mind to use any .NET assembly for it.

XEP-0126 specifies the best practices for implementing invisibility of presence.