除基本身份验证外，LdapConnection无法重新绑定

Question

我对这个有点失落。我在以下代码中调用.NET LdapConnection对象。第一个查询工作正常（SearchRequest），并使用默认的身份验证类型，协商。 在这个示例代码的foreach循环中，我然后尝试进行绑定以检查我在searchRequest中硬编码的用户的密码。
我在SearchResultEntry中获得了一个很好的DistinguishedName，并且Bind（）可以工作，但只能使用AuthType.Basic。没有其他选项可以工作，我也不热衷于使用Basic（不安全）身份验证。 想法？

        public LoginResult Authenticate(string userName, string password)
    {

        LdapDirectoryIdentifier identifier = new LdapDirectoryIdentifier(_serverName, _port);
        NetworkCredential credential = new NetworkCredential(_ServerUsername, _Serverpwd);
        LdapConnection ldapConnection = new LdapConnection(identifier, credential);
        ldapConnection.Timeout = new TimeSpan(0, 0, _timeout);

        try
        {
            SearchRequest searchRequest = new SearchRequest
                (_distinguisedName,
                 "(&(objectClass=user)(givenname=Joe)(sn=Smith))",
                 SearchScope.Subtree,
                 null);

            // cast the returned directory response as a SearchResponse object
            SearchResponse searchResponse =
                (SearchResponse)ldapConnection.SendRequest(searchRequest);

            // enumerate the entries in the search response
            foreach (SearchResultEntry entry2 in searchResponse.Entries)
            {
                // Check password by rebinding connection
                ldapConnection.AuthType = AuthType.Basic;
                ldapConnection.Bind(new NetworkCredential(entry2.DistinguishedName, password));
            }


        }
        catch (Exception e)
        {
            return LoginResult.Failure;
        }
        finally
        {
            ldapConnection.Dispose();
        }

        return LoginResult.Success;

    }