The GetUserName function returns the user name portion of a SIP URI.
string GetUserName( string uri );
Returns the user name as a string. Returns null if requested data is not found or if the URI passed in is not a valid SIP URI in the form specified above. Live Communications Server 2003 applications that pass non-SIP URI strings to this function need to be modified to work properly with Office Communications Server 2007 R2.
The user name occurs in a SIP URI before the host name, separated by an "@" (at) symbol. For example, a URI specified as "sip:firstname.lastname@example.org" would have a user name of "someone".