public class DirectoryEntryEqualityComparer : IEqualityComparer<DirectoryEntry>
    {
        public bool Equals(DirectoryEntry e1, DirectoryEntry e2)
        {
            return e1.Properties["distinguishedName"].Value == e2.Properties["distinguishedName"].Value;
        }

        public int GetHashCode(DirectoryEntry entry)
        {
            return entry.Properties["distinguishedName"].Value.GetHashCode();
        }
    }