c# – 使用backgroundWorker下载文件

发布时间：2020-12-16 01:47:10 所属栏目：百科来源：网络整理

导读：我创建了下载程序文件 private void btnTestDownload_Click(object sender,EventArgs e){backgroundWorker1.RunWorkerAsync();} 和工作！但 private void btnTestDownload_Click(object sender,EventArgs e){backgroundWorker1.CancelAsync();} backgroundWo

我创建了下载程序文件

private void btnTestDownload_Click(object sender,EventArgs e)
{
backgroundWorker1.RunWorkerAsync();
}

和工作！但

private void btnTestDownload_Click(object sender,EventArgs e)
{
backgroundWorker1.CancelAsync();
}

backgroundWorker dos不停！

解决方法

听起来你对背景工作者的目的有完全错误的想法.如果要同步下载单个文件并取消它,则所有这些功能都内置在WebClient类中.

后台工作者是长期运行的任务,总的来说,处理器密集.例如,如果您下载的文件是一个大文本文件,并且您需要解析文本文件的每一行,则可以使用后台工作程序,例如

下载文件

WebClient Client = new WebClient();

    public void TestStart()
    {
        //Handle the event for download complete
        Client.DownloadDataCompleted += Client_DownloadDataCompleted;
        //Start downloading file
        Client.DownloadDataAsync(new Uri("http://mywebsite.co.uk/myfile.txt"));
    }

    void Client_DownloadDataCompleted(object sender,DownloadDataCompletedEventArgs e)
    {
        //Remove handler as no longer needed
        Client.DownloadDataCompleted -= Client_DownloadDataCompleted;
        //Get the data of the file
        byte[] Data = e.Result;
    }
    public void TestCancel()
    {
        Client.CancelAsync();
        Client.DownloadDataCompleted -= Client_DownloadDataCompleted;
    }

处理文件

BackgroundWorker worker = new BackgroundWorker() { WorkerSupportsCancellation = true };

    //Take a stream reader (representation of a text file) and process it asyncronously
    public void ProcessFile(StreamReader Reader)
    {
        worker.DoWork += worker_DoWork;
        worker.RunWorkerAsync(Reader);
    }
    public void CancelProcessFile()
    {
        worker.CancelAsync();
    }

    void worker_DoWork(object sender,DoWorkEventArgs e)
    {
        //Get the reader passed as an argument
        StreamReader Reader = e.Argument as StreamReader;
        if (Reader != null)
        {
            //while not at the end of the file and cancellation not pending
            while (Reader.Peek() != -1 && !((BackgroundWorker)sender).CancellationPending)
            {
                //Read the next line
                var Line = Reader.ReadLine();
                //TODO: Process Line
            }
        }
    }

（编辑：李大同）

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