I have multi session on Citrix machine and I need to extract the FQDN\UPN of each of the users.

I use:

WTSQuerySessionInformation(..,.., WTSDomainName);

but it gives me partial\short string of the Domain, for example: DomainName instead of DomainName.com
- No Suffix!

How can I retrieve the full representation (active directory) of the domain name??

Thank you.