FTP删除:
FtpWebRequest request = (FtpWebRequest)WebRequest.Create("ftp://111.67.192.127/Data/2021年12月28日_test1.db");
request.Credentials = new NetworkCredential("用户名", "密码");
request.Method = WebRequestMethods.Ftp.DeleteFile;
FtpWebResponse response = (FtpWebResponse)request.GetResponse();
MessageBox.Show($"{response.StatusDescription}");