c# LDAP 验证

using System;using System.Text;using System.Collections;using System.DirectoryServices;namespace FormsAuth{  public class LdapAuthentication  {    private string _path;    private string _filterAttribute;    public LdapAuthentication(string path)    {      _path = path;    }    public bool IsAuthenticated(string domain, string username, string pwd)    {      string domainAndUsername = domain + @"\" + username;      DirectoryEntry entry = new DirectoryEntry(_path, domainAndUsername, pwd);      try      {        //Bind to the native AdsObject to force authentication.        object obj = entry.NativeObject;        DirectorySearcher search = new DirectorySearcher(entry);        search.Filter = "(SAMAccountName=" + username + ")";        search.PropertiesToLoad.Add("cn");        SearchResult result = search.FindOne();        if(null == result)        {          return false;        }        //Update the new path to the user in the directory.        _path = result.Path;        _filterAttribute = (string)result.Properties["cn"][0];      }      catch (Exception ex)      {        throw new Exception("Error authenticating user. " + ex.Message);      }      return true;    }    public string GetGroups()    {      DirectorySearcher search = new DirectorySearcher(_path);      search.Filter = "(cn=" + _filterAttribute + ")";      search.PropertiesToLoad.Add("memberOf");      StringBuilder groupNames = new StringBuilder();      try      {        SearchResult result = search.FindOne();        int propertyCount = result.Properties["memberOf"].Count;        string dn;        int equalsIndex, commaIndex;        for(int propertyCounter = 0; propertyCounter < propertyCount; propertyCounter++)        {          dn = (string)result.Properties["memberOf"][propertyCounter];       equalsIndex = dn.IndexOf("=", 1);          commaIndex = dn.IndexOf(",", 1);          if(-1 == equalsIndex)          {            return null;          }          groupNames.Append(dn.Substring((equalsIndex + 1), (commaIndex - equalsIndex) - 1));          groupNames.Append("|");        }      }    catch(Exception ex)    {      throw new Exception("Error obtaining group names. " + ex.Message);    }    return groupNames.ToString();  }}}