DirectorySearcher not returning any results from LDAP query (C#)

Question

I am trying to return all of the users in 2 OUs. The first OU (below) is IT Users within the HSD Users OU. This returns null every time, but I can get all of the users back with the following.

search.Filter = "(&(objectClass=user))";

I have tried many variations of the OU and DC in combination with no results.

 string DomainPath = "LDAP://hs.domain.org";
                DirectoryEntry searchRoot = new DirectoryEntry(DomainPath);
                DirectorySearcher search = new DirectorySearcher(searchRoot);
                //The following filter does work
                //search.Filter = "(&(objectClass=user))";

                search.Filter = string.Format("(&(objectClass=user)(OU=IT Users,OU=HSD Users,DC=hs,DC=domain,DC=org)");
                search.PropertiesToLoad.Add("samaccountname");
                search.PropertiesToLoad.Add("mail");
                search.PropertiesToLoad.Add("usergroup");
                search.PropertiesToLoad.Add("displayname");//first name
                search.PropertiesToLoad.Add("manager");


                SearchResult result;
                SearchResultCollection resultCol = search.FindAll();
                if (resultCol != null)
                {
                    for (int counter = 0; counter < resultCol.Count; counter++)

Answer 1

The LDAP filter you use is invalid, hence no records are returned. To locate objects in a particular container/OU or sub-tree, you need to set searchRoot to the path.

To find all entries contained directly in a specific container/OU, set the SearchScope to 1 (OneLevel) with the following constructor:

DirectorySearcher(DirectoryEntry, String, String[], SearchScope)

If you want to find all matching entries under a specific container/OU, then you can use the constructor above but use the specific container/OU as your searchRoot.