我正在尝试获取某个网页的html代码，我有一个正确的用户名和密码，但我仍然无法使用它，这是我的代码:privatevoidbuttondownloadfile_Click(objectsender,EventArgse){NetworkCredentialsnc=newNetworkCredentials("?","?","http://cdrs.globalpopsvoip.com/0000069/20091229/20091228_20091228.CDR");WebClientclient=newWebClient();client.Credentials=nc;Stringht