Question

I’m using the System.DirectoryServices library to query against a LDAP directory. I’m seeing all the text attributes fine, but I need to retrieve some operational attributes like pwdChangedTime. I get an object not set to an instance of the object’ type error when trying to get these properties.

using (DirectorySearcher search = new DirectorySearcher(dirCon,
                    ldapSearchFilter.Replace("{cn}", cn),
                    new string[] {"*","+"},
                    SearchScope.Subtree))
{
   foreach (SearchResult sr in search.FindAll())
   {
       la = new LdapAccount();
       la.pswdUpdateTime = DateTime.ParseExact(sr.GetDirectoryEntry().Properties["pwdchangedtime"].ToString(), dateFormat, null);
...
}

I see all the text attributes but it won’t find any operational attributes.

Answer 1

Doing some testing locally I see the property pwdlastset on the SearchResult, so I wonder if the property names are not what you expect them to be.

result.Properties["pwdlastset"]

There is also a PropertyNames collection on the SearchResult Properties collection that might be useful. Also, when I have queried AD before I did not call GetDirectoryEntry() but just enumerated the properties directly from the SearchResult.