获取ftp中目录的最后修改日期

Question

我如何获取最近使用C＃通过ftp修改目录的时间

我尝试了这个，没有运气

FtpWebRequest ftpRequest = (FtpWebRequest)WebRequest.Create(new Uri("ftp://" + ftpAddress + "/" + "public_html" + "/" + this.Url)); 
ftpRequest.Credentials = new NetworkCredential(FTPUsername, FTPPassword); 
ftpRequest.Method = WebRequestMethods.Ftp.GetDateTimestamp; 
DateTime FtpFileLastModified = ((FtpWebResponse)ftpRequest.GetResponse()).LastModified; 
return FtpFileLastModified;