ldap - OpenDSObject C# equivalent? -

i have old vb script uses opendsobject -

opendsobject("ldap://server:389/dc=com/dc=domain/ou=organizational unit/uid=" & user & "","cn=common name","password",ads_secure_authentication)

i trying convert c#. using directoryentry class.

directoryentry uentry = new directoryentry( "ldap://server:389/dc=com/dc=domain/ou=organizational unit" );  uentry.username = "common name"; uentry.password = "password"; 

i getting authentication error.
username property need sam name?
can use common name directory entry method?