ftp下载

通过这样写ftp下载。但是我要的是filePath 路径是自定义路径
就需要弹出保存框选择路径
请问各位。这个怎么实现。
FtpWebRequest reqFTP;
            try
            {
                FileStream outputStream = new FileStream(filePath + "\\" + fileName, FileMode.Create);
                reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri(ftpURI + fileName));
                reqFTP.Method = WebRequestMethods.Ftp.DownloadFile;
                reqFTP.UseBinary = true;
                reqFTP.Credentials = new NetworkCredential(ftpUserID, ftpPassword);
                FtpWebResponse response = (FtpWebResponse)reqFTP.GetResponse();
                Stream ftpStream = response.GetResponseStream();
                long cl = response.ContentLength;
                int bufferSize = 2048;
                int readCount;
                byte[] buffer = new byte[bufferSize];
                readCount = ftpStream.Read(buffer, 0, bufferSize);
                while (readCount > 0)
                {
                    outputStream.Write(buffer, 0, readCount);
                    readCount = ftpStream.Read(buffer, 0, bufferSize);
                }
                ftpStream.Close();
                outputStream.Close();
                response.Close();
            }
            catch (Exception ex)
            {
                //Insert_Standard_ErrorLog.Insert("FtpWeb", "Download Error --> " + ex.Message);
            }