如何检查FTP中存在的文件c＃

Question

我在FTP服务器中每20分钟创建一次，然后在一定时间后删除。我想在创建之后和删除之前下载文件。我喜欢

while (!File.Exists(reqFTP.RequestUri.ToString()))
                                    {
                                        if (DateTime.Now > timeout)
                                        {

                                        }
                                        Thread.Sleep(TimeSpan.FromSeconds(1));
                                    }

但是每次File.Exists返回false都没有运气。这是完整的代码

string uri = "ftp://" + dtr["FTP_SERVER"].ToString() + "/" + remoteftppath;
                                    Uri serverUri = new Uri(uri);
                                    if (serverUri.Scheme != Uri.UriSchemeFtp)
                                    {
                                        return;
                                    }
                                    var timeout = DateTime.Now.Add(TimeSpan.FromMinutes(1));

                                    FtpWebRequest reqFTP;
                                    reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri("ftp://" + dtr["FTP_SERVER"].ToString() + "/" + remoteftppath));
                                    reqFTP.Credentials = new NetworkCredential(dtr["FTP_USER_ID"].ToString(), dtr["FTP_PASSWORD"].ToString());
                                    reqFTP.KeepAlive = false;
                                    reqFTP.Method = WebRequestMethods.Ftp.DownloadFile;
                                    reqFTP.UseBinary = true;
                                    reqFTP.Proxy = null;
                                    reqFTP.UsePassive = false;
                                    while (!File.Exists(reqFTP.RequestUri.ToString()))
                                    {
                                        if (DateTime.Now > timeout)
                                        {

                                        }
                                        Thread.Sleep(TimeSpan.FromSeconds(1));
                                    }
                                    FtpWebResponse response = (FtpWebResponse)reqFTP.GetResponse();
                                    responseStream = response.GetResponseStream();

我不知道出了什么问题。它根本没有从循环中出来