Question

 private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
    {            
        int currentProgress=-1;

        while (currentProgress<length)
        {
            currentProgress=Worker.progress;
            backgroundWorker1.ReportProgress(currentProgress);
            Thread.Sleep(500);
            length = Worker.UrlList.Count;
        }
    }

    private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
    {
        int ix = e.ProgressPercentage;
        progressBar1.Value = ix;
        lblText.Text =ix+" %";
    }

我写了一个程序，通过阅读文件下载页面源有大约1000个URL。所以我用Tasks来下载异步页面。这里Worker.progress是当前执行的URL数量。虽然debuger击中backgroundWorker1.ReportProgress(currentProgress);，但它永远不会进入backgroundWorker1_ProgressChanged。

 private void StartButton_Click(object sender, EventArgs e)
    {            
        t.makeUrlList(inputFile);

        backgroundWorker1 = new BackgroundWorker();
        backgroundWorker1.WorkerReportsProgress = true;
        backgroundWorker1.DoWork += backgroundWorker1_DoWork;
        backgroundWorker1.ProgressChanged += backgroundWorker1_ProgressChanged;
        backgroundWorker1.RunWorkerAsync();
        t.RunTasks();
        Application.Exit();
    }

后台工作人员在启动按钮点击时初始化...

这是创建我的任务的地方....

public void RunTasks()
    {
        if (numOfTasks > UrlList.Count)
            numOfTasks=UrlList.Count-1;
       Task[] t = new Task[numOfTasks];
        int j = 0;
        while ( j < UrlList.Count-1)
        {

           for (int i = 0; (i < t.Count())&&(j<UrlList.Count-1); i++)
            {


                try
                {
                    if (t[i].IsCompleted || t[i].IsCanceled || t[i].IsFaulted)
                    {
                        t[i] = Task.Run(() => FindWIN(j));
                        j++;
                        progress = j;                            
                    }
                }
                catch (NullReferenceException ex)
                {
                    t[i] = Task.Run(() => FindWIN(j));
                    j++;
                    progress = j;
                }
                }
            }
        }

Answer 1

如果您希望BackgroundWorker支持更新进度信息，则应将WorkerReportsProgress的值设置为true。如果此属性为true，则用户代码可以调用ReportProgress来启动事件ProgressChanged。

后台工作程序初始化： -

 backgroundWorker1 = new BackgroundWorker();
 backgroundWorker1.WorkerReportsProgress = true;
 backgroundWorker1.DoWork+=backgroundWorker1_DoWork;
 backgroundWorker1.ProgressChanged+=backgroundWorker1_ProgressChanged;
 backgroundWorker1.RunWorkerAsync();

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
            int currentProgress = -1;

            decimal length=1000;
            while (currentProgress < length)
            {
                currentProgress = Worker.progress;
                backgroundWorker1.ReportProgress(currentProgress);
                Thread.Sleep(500);
                length = Worker.UrlList.Count;
            }
 }

private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)        {
            int ix = e.ProgressPercentage;
            progressBar1.Value = ix;
            lblText.Text = ix + " %";
}

Answer 2

在初始化阶段，您应该将worker的WorkerReportsProgress属性设置为true。

Answer 3

请参阅下面的演示代码。这大多是未经测试的，当然不是生产标准，但它应该会给你一个良好的开端！

它使用ConcurrentQueue来保存要处理的网址列表。这是线程安全的，让生活更轻松。
它具有可配置数量的网址和任务。最好不要完成1000个任务，而是拥有一个工作项队列，以及一个较小的任务池，它可以提取项目＆＃39;离开队列，直到它排空。这意味着您可以对不同数量的任务进行性能测试，并为您的问题找到最佳价值。
更新进度条时使用Invoke - 这可以避免跨线程异常。

否BackgroundWorker - 仅TaskFactory和Task

public partial class Form1 : Form
{
    private const int UrlCount = 1000;
    private const int taskCount = 10;
    private ConcurrentQueue<string> urlList;
    private List<Task> taskList;

    public Form1()
    {
        InitializeComponent();
    }

    private void ResetQueue()
    {
        // fake up a number of strings to process
        urlList = new ConcurrentQueue<string>(Enumerable.Range(0, UrlCount)
                  .Select(i => "http://www." + Guid.NewGuid().ToString() + ".com"));
    }

    private void button1_Click(object sender, EventArgs e)
    {
        ResetQueue();
        var taskFactory = new TaskFactory();
        // start a bunch of tasks
        taskList = Enumerable.Range(0, taskCount).Select(i => taskFactory.StartNew(() => ProcessUrl()))
                              .ToList();
    }

    void ProcessUrl()
    {
        string current;

        // keep grabbing items till the queue is empty
        while (urlList.TryDequeue(out current))
        {
            // run your code
            FindWIN(current);

            // invoke here to avoid cross thread issues
            Invoke((Action)(() => UpdateProgress()));
        }
    }

    void FindWIN(string url)
    {
        // your code here
        // as a demo, sleep a sort-of-random time between 0 and 100 ms
        Thread.Sleep(Math.Abs(url.GetHashCode()) % 100);
    }

    void UpdateProgress()
    {
        // work out what percentage of the queue is processed
        progressBar1.Value = (int)(100 - ((double)urlList.Count * 100.0 / UrlCount));
    }
}

ReportProgress不会使用c＃中的任务调用progressChanged

3 个答案: