How to list all computers and the last time they were logged onto in AD?

Question

I am trying to retrieve a list of Computer Names and the date they were last logged onto from Active Directory and return them in a datatable. Getting the names is easy enough but when I try to add the "lastLogon" or "lastLogonTimestamp" like shown below, the only values I get for the lastLogonTimestamp is "System._ComObject"

public DataTable GetListOfComputers(string domainName)
{
  DirectoryEntry entry = new DirectoryEntry("LDAP://DC=" + domainName + ",DC=com");
  DirectorySearcher search = new DirectorySearcher(entry);
  string query = "(objectclass=computer)";
  search.Filter = query;

  search.PropertiesToLoad.Add("name");
  search.PropertiesToLoad.Add("lastLogonTimestamp");

  SearchResultCollection mySearchResultColl = search.FindAll();

  DataTable results = new DataTable();
  results.Columns.Add("name");
  results.Columns.Add("lastLogonTimestamp");

  foreach (SearchResult sr in mySearchResultColl)
  {
    DataRow dr = results.NewRow();
    DirectoryEntry de = sr.GetDirectoryEntry();
    dr["name"] = de.Properties["Name"].Value;
    dr["lastLogonTimestamp"] = de.Properties["lastLogonTimestamp"].Value;
    results.Rows.Add(dr);
    de.Close();
  }

  return results;
}

If I query AD using a tool like LDP I can see that the property exists and is populated with data. How can I get at this info?

Answer 1

It'd be easier to use the ComputerPrincipal class and a PrincipalSearcher from System.DirectoryServices.AccountManagement.

PrincipalContext pc = new PrincipalContext(ContextType.Domain, domainName);
PrincipalSearcher ps = new PrincipalSearcher(new ComputerPrincipal(pc));
PrincipalSearchResult<Principal> psr = ps.FindAll();
foreach (ComputerPrincipal cp in psr)
{
    DataRow dr = results.NewRow();
    dr["name"] = cp.Name;
    dr["lastLogonTimestamp"] = cp.LastLogon;    
    results.Rows.Add(dr);
}