c# - System.DirectoryServices慢吗？

当用户登录网站时，我使用下面的代码在active directory中查找信息。在本地域上运行非常快，但是在vpn上运行到远程受信任域上非常慢（大约需要7或8秒）。从同一个框向远程域运行dsa.msc几乎与在本地运行dsa.msc一样快。
我正在使用属性筛选来检索尽可能少的数据量，那么在这种情况下，System.DirectoryServices是否存在固有的速度慢的问题，或者是否有人对如何提高性能有任何提示？
通过vpn的网络连接很好，只有这段代码运行得很慢。

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

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            using (var LDAPConnection = new DirectoryEntry("LDAP://domain/dc=domain,dc=com", "username", "password"))
            {
                LDAPConnection.AuthenticationType = AuthenticationTypes.Secure;
                using (DirectorySearcher Searcher = new DirectorySearcher(LDAPConnection))
                {
                    Searcher.Filter = "(&(&(objectclass=user)(objectcategory=person))sAMAccountName=username)";
                    Searcher.PropertiesToLoad.Add("mail");

                    SearchResult result = Searcher.FindOne(); //this line takes ages!

                    string EmailAddress = result.Properties["mail"][0].ToString();
                    Console.WriteLine(EmailAddress);
                }
            }
        }
    }
}

最佳答案

另一个建议是直接使用System.DirectoryServices.Protocols；您的代码将如下所示：

string filter = "(&(&(objectclass=user)(objectcategory=person))" +
                "sAMAccountName=username)";
NetworkCredential credentials = new NetworkCredential(...);
LdapDirectoryIdentifier directoryIdentifier =
   new LdapDirectoryIdentifier("server", 389, false, false);
using (LdapConnection connection =
   new LdapConnection(directoryIdentifier, credentials, AuthType.Basic))
{
    connection.Timeout = new TimeSpan(0, 0, 30);
    connection.SessionOptions.ProtocolVersion = 3;
    SearchRequest search =
        new SearchRequest(query, filter, SearchScope.Base, "mail");
    SearchResponse response = connection.SendRequest(search) as SearchResponse;
    foreach(SearchResultEntry entry in response.Entries)
    {
        Console.WriteLine(entry.Attributes["mail"][0]);
    }
}