IAdmSearchResultIterator

[Reflection.Assembly]::LoadWithPartialName("Softerra.Adaxes.Adsi")

$ouDN = "OU=Contacts,DC=domain,DC=com"

# Connect to the Adaxes service.
$ns = New-Object "Softerra.Adaxes.Adsi.AdmNamespace"
$service = $ns.GetServiceDirectly("localhost")

# Bind to the organizational unit.
$searcher = $service.OpenObject("Adaxes://$ouDN", $null, $null, 0)

# Specify search parameters.
$searcher.Criteria = New-AdmCriteria "contact"
$searcher.SearchScope = "ADS_SCOPE_SUBTREE"
$searcher.PageSize = 500 # Search results per page.

try
{
    # Execute search.
    $searchResultIterator = $searcher.ExecuteSearch()
    
    $totalCount = 0
    while($true)
    {
        # Get the next page of search results.
        $searchResults = $searchResultIterator.GetNextPage()
        if (($searchResults.Length -eq 0) -and ($searchResultIterator.IsSearchCompleted))
        {
            break # No more results to return.
        }
        
        $totalCount += $searchResults.Length
        foreach ($searchResult in $searchResults)
        {
            Write-Host $searchResult.Name
        }

        Start-Sleep -Milliseconds 0
    }

    Write-Host
    Write-Host "Contacts found: $totalCount"
}
finally
{
    # Release resources used by the search.
    $searchResultIterator.Dispose()
}

using System;
using System.Threading;
using Softerra.Adaxes.Adsi;
using Softerra.Adaxes.Interop.Adsi;
using Softerra.Adaxes.Directory.Criteria;
using Softerra.Adaxes.Interop.Adsi.PersistentObjects;

class Program
{
    static void Main(string[] args)
    {
        const string ouPath = "Adaxes://OU=Contacts,DC=domain,DC=com";

        // Connect to the Adaxes service.
        AdmNamespace ns = new AdmNamespace();
        IAdmService service = ns.GetServiceDirectly("localhost");

        // Bind to the organizational unit.
        IAdmDirectorySearcher searcher = (IAdmDirectorySearcher)service.OpenObject(
            ouPath, null, null, 0);

        // Build search criteria.
        Criteria criteria = new();
        criteria.AddType("contact");

        // Specify search parameters.
        searcher.Criteria = criteria;
        searcher.SearchScope = ADS_SCOPEENUM.ADS_SCOPE_SUBTREE;
        searcher.PageSize = 500; // Search results per page.

        // Execute search.
        using (IAdmSearchResultIterator searchResultIterator =
                (IAdmSearchResultIterator)searcher.ExecuteSearch())
        {
            int totalCount = 0;
            while (true)
            {
                // Get the next page of search results.
                AdmSearchResult[] searchResults = searchResultIterator.GetNextPage();
                if ((searchResults.Length == 0) && (searchResultIterator.IsSearchCompleted))
                {
                    break; // No more results to return.
                }
                
                totalCount += searchResults.Length;
                foreach (AdmSearchResult searchResult in searchResults)
                {
                    Console.WriteLine(searchResult.Name);
                }

                Thread.Sleep(0);
            }

            Console.WriteLine();
            Console.WriteLine($"Contacts found: {totalCount}");
        }
    }
}