Retrieve Large LDAP Multi-valued Attributes

/// <summary>
/// Listing 6.8 - Range Expansion method used for large attributes.
/// </summary>
/// <param name="entry"></param>
/// <param name="attribute"></param>
/// <returns></returns>
/// <example>
/// <code>
/// ArrayList members = RangeExpansion(group, "member");
/// </code>
/// </example>
/// <remarks>Addison Wesley - The .NET Developer's Guide to Directory Services Programming</remarks>
public static ArrayList RangeExpansion(DirectoryEntry entry, string attribute)
{
    ArrayList al = new ArrayList(5000);
    int idx = 0;

    // zero based index, so less 1
    int step = entry.Properties[attribute].Count - 1;

    string range = String.Format("{0};range={{0}}-{{1}}", attribute);

    string currentRange = String.Format(range, idx, step);

    DirectorySearcher ds = new DirectorySearcher(
        entry,
        String.Format("({0}=*)", attribute),
        new string[] { currentRange },
        System.DirectoryServices.SearchScope.Base
    );

    bool lastSearch = false;
    SearchResult sr = null;

    while (true)
    {
        if (!lastSearch)
        {
            ds.PropertiesToLoad.Clear();
            ds.PropertiesToLoad.Add(currentRange);

            sr = ds.FindOne();
        }

        if (sr != null)
        {
            if (sr.Properties.Contains(currentRange))
            {
                foreach (object dn in sr.Properties[currentRange])
                {
                    al.Add(dn);
                    idx++;
                }

                // our exit condition
                if (lastSearch)
                {
                    break;
                }

                currentRange = String.Format(range, idx, (idx + step));

            }
            else
            {

                // one more search
                lastSearch = true;
                currentRange = String.Format(range, idx, "*");
            }
        }
        else
        {
            break;
        }
    }

    return al;
}


//
// Unit test
// --------------------------------------------------------------------------

/// <summary>
/// Shows how to use Listing 6.8
/// </summary>
[Test]
public void EnumerateLargeAttributes()
{
    // point this to a big group in your directory (TestUtils.Settings.DefaultPartition == "dc=domain,dc=com")
    DirectoryEntry bigGroup = TestUtils.CreateDirectoryEntry("CN=Ranged Group,CN=Roles," + TestUtils.Settings.DefaultPartition);

    using (bigGroup)
    {
        foreach (string s in RangeExpansion(bigGroup, "member"))
        {
            Console.WriteLine(s);
        }
    }
}

//
// TestUtils.cs
// --------------------------------------------------------------------------

using System;
using System.Collections.Generic;
using System.Text;
using System.DirectoryServices;

using DotNetDevGuide.DirectoryServices.Configuration;

namespace DotNetDevGuide.DirectoryServices
{
    class TestUtils
    {
        static LdapSettings settings;

        static TestUtils()
        {
            settings = System.Configuration.ConfigurationSettings.GetConfig("LdapSettings") as LdapSettings;

            if (settings == null)
                throw new InvalidOperationException("Invalid Configuration Specified");
        }

        public static LdapSettings Settings
        {
            get { return settings; }
        }

        /// <summary>
        /// Retrieves a DirectoryEntry using configuration data
        /// </summary>
        /// <param name="path"></param>
        /// <returns></returns>
        public static DirectoryEntry CreateDirectoryEntry(string path)
        {
            //I am intentionally not checking a bunch of stuff for input validation
            //because this is just test harness and I don't care if you screw it up too much

            AuthenticationTypes bindingAuth = AuthenticationTypes.Secure;

            switch (settings.Protection)
            {
                //typical for non-SSL ADAM - so assuming server specified
                case ConnectionProtection.None:
                    bindingAuth = AuthenticationTypes.None;
                    break;

                //typical for AD
                case ConnectionProtection.Secure:
                    bindingAuth = AuthenticationTypes.Secure | AuthenticationTypes.Sealing | AuthenticationTypes.Signing;
                    break;

                //typical for SSL-ADAM (assuming server specified as well)
                case ConnectionProtection.SSL:
                    bindingAuth = AuthenticationTypes.SecureSocketsLayer;
                    break;
            }

            if (!String.IsNullOrEmpty(settings.Server))
                bindingAuth = bindingAuth | AuthenticationTypes.ServerBind;

            return new DirectoryEntry(
                BuildAdsPath(path),
                settings.Username,
                settings.Password,
                bindingAuth
                );
        }

        /// <summary>
        /// Creates a DirectoryEntry from the DefaultPartition defined in config
        /// </summary>
        /// <returns></returns>
        public static DirectoryEntry GetDefaultPartition()
        {
            return CreateDirectoryEntry(settings.DefaultPartition);
        }

        /// <summary>
        /// Simple method to find and return a user using the CN name and searching the
        /// defaultNamingContext defined in config.
        /// </summary>
        /// <param name="userRDN"></param>
        /// <returns></returns>
        public static DirectoryEntry FindUserByCN(string userRDN)
        {
            using (DirectoryEntry searchRoot = GetDefaultPartition())
            {
                DirectorySearcher ds = new DirectorySearcher(
                    searchRoot,
                    String.Format("(cn={0})", userRDN),
                    new string[] { "cn" },
                    SearchScope.Subtree
                    );

                SearchResult sr = ds.FindOne();

                return (sr != null) ? sr.GetDirectoryEntry() : null;
            }
        }

        /// <summary>
        /// We use this take into account whether we have a server or not
        /// </summary>
        /// <param name="path"></param>
        /// <returns></returns>
        public static string BuildAdsPath(string path)
        {
            return String.Format("LDAP://{0}{1}", String.IsNullOrEmpty(settings.Server) ? String.Empty : settings.Server + "/", path);
        }
    }
}