WSS : Interop.ActiveDs missing

[yohanb]

Hello,

i have created a webpart for Windows Sharepoint Services in c# that
converts netbios username (domain\user) in DN ( AD format) using
"ActiveDs" dll in the goal to bind to an Active Directory user object.

Ex of code using ActiveDs :

#
ActiveDs.NameTranslateClass trans = new ActiveDs.NameTranslateClass();
#

I have compiled my project and deployed it succeffuly on my server with
STSADM but when i would like to display the page with my webpart in it,
i have the error :

File or assembly not found : Interop.ActiveDs

any idea ?
Thank you in advance.

yohan