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.

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