bw = new BackgroundWorker();
                                            bw.WorkerReportsProgress = true;
                                            bw.DoWork += new DoWorkEventHandler(bw_DoWork);
                                            bw.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bw_RunWorkerCompleted);
                                            bw.ProgressChanged += new ProgressChangedEventHandler(bw_ProgressChanged);
                                            bw.RunWorkerAsync(temp);
private void bw_DoWork(object sender, DoWorkEventArgs e)
        {
            ftp 下载
        }

------解决方案--------------------
比如用webclient

C# code

        WebClient wc = new WebClient();
        byte[] data = new byte[10];
        wc.UploadDataCompleted += new UploadDataCompletedEventHandler(wc_UploadDataCompleted);
        wc.UploadDataAsync(new Uri("http://www.sina.com.cn"), data);