How to connect to Active Directory via LDAPS in C#?

https://stackoverflow.com/questions/34813550/how-to-connect-to-active-directory-via-ldaps-in-c

You need to specify the port, since 636 is the default LDAPS port.

new DirectoryEntry("LDAP://192.168.2.59:636", USER, PWD)

I do this in some of my code, and using "LDAP://" (not "LDAPS://") is what works.

If that doesn't work, then there may be a certificate error. You can test this with a browser. If you use Chrome, open Chrome with this (so it lets you use port 636):

"C:\Program Files (x86)\Google\Chrome\Application\chrome.exe" --explicitly-allowed-ports=636

Then go to https://192.168.2.59:636. If you get a big fancy certificate error, then the problem is that the certificate is not trusted. View the certificate from Chrome and see what the problem is. It could be issued by an authority that is not in the Windows cert store.