在做FTP服务器文件上传的时候，要判断文件夹是否存在，代码在走到：ftp.GetResponse()的时候，就会抛出异常：基础连接已经关闭: 服务器提交了协议冲突。

具体代码如下：

StringBuilder sb = new StringBuilder();
FtpWebRequest ftp;
ftp = (FtpWebRequest)FtpWebRequest.Create(new Uri(url));
ftp.Credentials = new NetworkCredential(ftpUserID, ftpPassword);
ftp.Method = WebRequestMethods.Ftp.ListDirectoryDetails;
ftp.KeepAlive = false;
WebResponse response = ftp.GetResponse();
StreamReader reader = new StreamReader(response.GetResponseStream());
string line = reader.ReadLine();
while (line != null)
{
sb.Append(line);
sb.Append("/n");
line = reader.ReadLine();
}
if (!string.IsNullOrEmpty(sb.ToString()))
{
sb.Remove(sb.ToString().LastIndexOf("/n"), 2);
result = sb.ToString().Split(new string[] { "/n" }, StringSplitOptions.RemoveEmptyEntries);
}
else
{
result = new string[] { };
}

reader.Close();
response.Close();

哪位大神能够给出解决办法呢？？非常急急急！！！