Active Directory authentication on the pages of the ASP .NET webapplication

 Hi.

I need some help.
I'm learning ASP .NET now, and meet some task I should to resolve.

For example we have a "simple" html page and two menus(vertical and horisontal).
My web application is using windows authentication.

If the user (logged to my webapp.) in the Administrators Active Directory group - vertical menu must be visible,
if the user in other("private_men" AD group, for example) - horisontal menu must be visible.

Question : How can I recognize the username and user Active Directory group, authenticated on the my web application? and then how I must to use this login/group to show/hide menus?

Do you know some MSDN links?

PS: If there're other branch for ASP .NET questions in this forum, please move my post.
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