System. DirectoryServices

System.DirectoryServices
https://www.nuget.org/packages/System.DirectoryServices

System.DirectoryServices.AccountManagement
https://www.nuget.org/packages/System.DirectoryServices.AccountManagement/4.5.0-preview1-25914-04

ActiveDirectory провайдер.

Validate a username and password against Active Directory?
https://stackoverflow.com/questions/290548/validate-a-username-and-password-against-active-directory

Creating Active Directory user with password in C#
https://stackoverflow.com/questions/2305857/creating-active-directory-user-with-password-in-c-sharp