gistfile1.cs

//For easy notification.
public interface NotifyLoaded
{
    void LoadComplete(ArrayList computersInDomain);
    void oneMore();
}
public static ArrayList getComputersInDomain(string domainName, NotifyLoaded countForm = null)
{
    System.Collections.ArrayList computers = new System.Collections.ArrayList();
    DirectoryEntry de = new DirectoryEntry("LDAP://" + domainName);
    DirectorySearcher mySearcher = new DirectorySearcher(de);
    mySearcher.Filter = ("(objectClass=computer)");
    mySearcher.PropertyNamesOnly = true;
    //For speed we only ask for one property that we will get back anyway.
    mySearcher.PropertiesToLoad.Add("adspath");
    mySearcher.SizeLimit = int.MaxValue;
    mySearcher.PageSize = int.MaxValue;
    SearchResultCollection src = mySearcher.FindAll();

    //HACKISH, but we are only searching one domain, so we can assume that the start value will be constant throughout the result set.
    int start = 0;
    if (src[0] != null)
        start = src[0].Path.IndexOf("CN=") + 3;
    //END HACKISH

    foreach (SearchResult c in src)
    {
        //Being delimited by commas, this is the fastest way to get the computer name.
        string name = c.Path.Substring(start).Split(',')[0]; 
        computers.Add(name);
        if (countForm != null)
            countForm.oneMore();
    }
    computers.Sort();
    if (countForm != null)
        countForm.LoadComplete(computers);
    return computers;
}