从 Parallel.ForEach 更新 UI

Question

我只是想更新Parallel.ForEach 中的进度条，应用程序似乎冻结了。

尽管我已经按照其他帖子的建议尝试使用Invoke 解决方案，但我仍然遇到问题。

这是我的代码的简化版本：

public partial class Form1 : Form
{
    event EventHandler ReportProgress;

    class ProgressEvent : EventArgs
    {
        public int Total { get; set; }
        public int Current { get; set; }
    }

    public Form1()
    {
        InitializeComponent();
        ReportProgress += Form1_ReportProgress;
    }

    private void Form1_ReportProgress( object sender, EventArgs e )
    {
        var progress = e as ProgressEvent;
        if ( InvokeRequired )
        {
            this.Invoke( new Action( () => { progressBar.Maximum = progress.Total; progressBar.Value = progress.Current; } ) );
        }
    }

    private void buttonStart_Click( object sender, EventArgs e )
    {
        // Create a list with seed to be used later
        List<int> values = new List<int>() { };
        values.AddRange( Enumerable.Range( 1, 15 ) );

        var total = values.Count();
        var current = 0;

        Parallel.ForEach( values, v =>
        {
            Interlocked.Increment( ref current );

            var r = new Random( v );
            // Just sleep a little
            var sleep = r.Next( 10, 1000 );
            Thread.Sleep( sleep );

            // Update the progress bar
            ReportProgress( null, new ProgressEvent() { Current = current, Total = total } );
        }
        );

        MessageBox.Show( "Done " );
    }
}

应用程序似乎挂起并且没有显示消息框，而如果我删除事件生成 (ReportProgress) 一切正常，但显然进度条根本没有更新。

Answer 1

你可以改变：

this.Invoke( new Action( () => { progressBar.Maximum = progress.Total; progressBar.Value = progress.Current; } ) );

到：

this.BeginInvoke( new Action( () => { progressBar.Maximum = progress.Total; progressBar.Value = progress.Current; } ) );

这将在异步线程上执行操作。

Answer 2

我编辑你的代码。如果您想屏幕不冻结，可能更简单的方法是使用后台工作人员执行操作。

当您使用后台工作时，UI线程不会被阻塞。因此，用户仍然可以与UI交互。

public partial class Form1 : Form
{
    event EventHandler ReportProgress;

    class ProgressEvent : EventArgs
    {
        public int Total { get; set; }
        public int Current { get; set; }
    }

    public Form1()
    {
        InitializeComponent();
        ReportProgress += Form1_ReportProgress;
    }

    private void Form1_ReportProgress(object sender, EventArgs e)
    {
        var progress = e as ProgressEvent;
        this.Invoke(new Action(() =>
                               {
                                   progressBar.Maximum = progress.Total;
                                   progressBar.Value = progress.Current;
                               }));
    }

    private void button1_Click(object sender, EventArgs e)
    {
        // Collect data from UI, I use list for example
        List<int> values = new List<int>() { };
        values.AddRange(Enumerable.Range(1, 100));

        BackgroundWorker backgroundWorker = new BackgroundWorker();
        backgroundWorker.DoWork += BackgroundWorkerOnDoWork;
        backgroundWorker.RunWorkerAsync(values);
    }

    private void BackgroundWorkerOnDoWork(object sender, DoWorkEventArgs doWorkEventArgs)
    {
        var values = (IEnumerable<int>) doWorkEventArgs.Argument; // the 'argument' parameter resurfaces here

        var total = values.Count();
        var current = 0;

        Parallel.ForEach(values, v =>
                                 {
                                     Interlocked.Increment(ref current);

                                     var r = new Random(v);
                                     // Just sleep a little
                                     var sleep = r.Next(10, 1000);
                                     Thread.Sleep(sleep);

                                     // Update the progress bar
                                     ReportProgress(null, new ProgressEvent() {Current = current, Total = total});
                                 }
                        );

        MessageBox.Show("Done ");
    }
}