using (DirectoryEntry de = new DirectoryEntry(ldapPath, ldapUsername, password, AuthenticationTypes.ServerBind)) {
    try {
        // Bind to the native AdsObject to force authentication.
        object obj = de.NativeObject;//not IDisposable
    } catch(...

* "LDAP://server.uri:636"
* "LDAP://insecure.server.uri:389"
* "LDAP://server.uri:636/cn=username,ou=staff,o=myOrganisation,c=org"

* "cn=username,ou=staff,o=myOrganisation,c=org"