从后台线程问题更新 UI

Question

I'm coding a class to move and copy files. I'm raising events when the current file progress and the total progress changes. When I test the code on my XP machine, it works fine, but when I run it on my Windows 7 64-Bit machine, the current progress doesn't update the UI correctly. The current progress ProgressBar only gets half way then starts on the next file which does the same. The total progress ProgressBar updates fine. Any ideas why this is happening?

EDIT: The Windows 7 machine is running a quad-core and the XP is running a dual-core. Not sure if that might be what's making a difference. I'm only a hobbyist so excuse my ignorance:)

EDIT: Code added (Background)

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.IO;
using System.Threading;
using System.Timers;
using Timer = System.Timers.Timer;

namespace nGenSolutions.IO
{
public class FileTransporter
{
    #region Delegates

    public delegate void CurrentFileChangedEventHandler(string fileName);

    public delegate void CurrentProgressChangedEventHandler(int      percentComplete);

    public delegate void CurrentWriteSpeedUpdatedEventHandler(long bytesPerSecond);

    public delegate void TotalProgressChangedEventHandler(int percentComplete);

    public delegate void TransportCompleteEventHandler(FileTransportResult result);

    #endregion

    private readonly List<string> _destinationFiles = new List<string>();
    private readonly List<string> _sourceFiles = new List<string>();

    private long _bytesCopiedSinceInterval;
    private FileTransportResult _result;

    private Timer _speedTimer;
    private long _totalDataLength;

    private BackgroundWorker _worker;

    public bool TransportInProgress { get; private set; }

    public event CurrentFileChangedEventHandler CurrentFileChanged;

    public event CurrentProgressChangedEventHandler CurrentProgressChanged;

    public event CurrentWriteSpeedUpdatedEventHandler CurrentWriteSpeedUpdated;

    public event TotalProgressChangedEventHandler TotalProgressChanged;

    public event TransportCompleteEventHandler TransportComplete;

    public void AddFile(string sourceFile, string destinationFile)
    {
        if (!File.Exists(sourceFile))
            throw new FileNotFoundException("The specified file does not exist!", sourceFile);

        var fileInfo = new FileInfo(sourceFile);

        _totalDataLength += fileInfo.Length;

        _sourceFiles.Add(sourceFile);
        _destinationFiles.Add(destinationFile);
    }

    public void BeginTransport()
    {
        // update the write speed every 3 seconds
        _speedTimer = new Timer {Interval = 3000};
        _speedTimer.Elapsed += SpeedTimerElapsed;

        _worker = new BackgroundWorker();
        _worker.DoWork += DoTransport;
        _worker.RunWorkerCompleted += WorkerCompleted;

        _worker.RunWorkerAsync();
        _speedTimer.Start();

        TransportInProgress = true;
    }

    private void SpeedTimerElapsed(object sender, ElapsedEventArgs e)
    {
        InvokeCurrentSpeedUpdated(_bytesCopiedSinceInterval);

        _bytesCopiedSinceInterval = 0;
    }

    private void WorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        TransportInProgress = false;
        InvokeTransportComplete(_result);
    }

    public void CancelTransport(bool rollbackChanges)
    {
        if (TransportInProgress == false)
            throw new InvalidOperationException("You tried to stop the transport before you started it!");

        _result = FileTransportResult.Cancelled;

        _worker.CancelAsync();

        while (_worker.IsBusy)
        {
            // wait for worker to die an 'orrible death
        }

        // TODO: rollback changes if requested
    }

    private void DoTransport(object sender, DoWorkEventArgs e)
    {
        long totalBytesCopied = 0;
        int totalPercentComplete = 0;

        for (int i = 0; i < _sourceFiles.Count; i++)
        {
            string sourceFile = _sourceFiles[i];
            string destinationFile = _destinationFiles[i];

            long currentFileLength = new FileInfo(sourceFile).Length;

            InvokeCurrentFileChanged(sourceFile);

            using (var sourceStream = new FileStream(sourceFile, FileMode.Open, FileAccess.Read))
            {
                using (var destinationStream = new FileStream(destinationFile, FileMode.Create, FileAccess.Write))
                {
                    using (var reader = new BinaryReader(sourceStream))
                    {
                        using (var writer = new BinaryWriter(destinationStream))
                        {
                            int lastPercentComplete = 0;

                            for (int j = 0; j < currentFileLength; j++)
                            {
                                writer.Write(reader.ReadByte());

                                totalBytesCopied += 1;
                                _bytesCopiedSinceInterval += 1;

                                int current = Convert.ToInt32((j/(double) currentFileLength)*100);
                                int total = Convert.ToInt32((totalBytesCopied/(double) _totalDataLength)*100);

                                // raise progress events every 3%
                                if (current%3 == 0)
                                {
                                    // only raise the event if the progress has increased
                                    if (current > lastPercentComplete)
                                    {
                                        lastPercentComplete = current;
                                        InvokeCurrentProgressChanged(lastPercentComplete);
                                    }
                                }

                                if (total%3 == 0)
                                {
                                    // only raise the event if the progress has increased
                                    if (total > totalPercentComplete)
                                    {
                                        totalPercentComplete = total;
                                        InvokeTotalProgressChanged(totalPercentComplete);
                                    }
                                }
                            }
                        }

                        InvokeCurrentProgressChanged(100);
                    }
                }
            }
        }

        InvokeTotalProgressChanged(100);
    }

    private void InvokeCurrentFileChanged(string fileName)
    {
        CurrentFileChangedEventHandler handler = CurrentFileChanged;

        if (handler == null) return;

        handler(fileName);
    }

    private void InvokeCurrentProgressChanged(int percentComplete)
    {
        CurrentProgressChangedEventHandler handler = CurrentProgressChanged;

        if (handler == null) return;

        handler(percentComplete);
    }

    private void InvokeCurrentSpeedUpdated(long bytesPerSecond)
    {
        CurrentWriteSpeedUpdatedEventHandler handler = CurrentWriteSpeedUpdated;

        if (handler == null) return;

        handler(bytesPerSecond);
    }

    private void InvokeTotalProgressChanged(int percentComplete)
    {
        TotalProgressChangedEventHandler handler = TotalProgressChanged;

        if (handler == null) return;

        handler(percentComplete);
    }

    private void InvokeTransportComplete(FileTransportResult result)
    {
        TransportCompleteEventHandler handler = TransportComplete;

        if (handler == null) return;

        handler(result);
    }
}

}

EDIT: Code added (GUI)

using System;
using System.IO;
using System.Windows.Forms;
using ExtensionMethods;
using nGenSolutions.IO;

namespace TestApplication
{
public partial class ProgressForm : Form
{
    public ProgressForm()
    {
        InitializeComponent();
    }

    private void ProgressForm_Load(object sender, EventArgs e)
    {
        var transporter = new FileTransporter();
        foreach (string fileName in Directory.GetFiles("C:\\Temp\\"))
        {
            transporter.AddFile(fileName, "C:\\" + Path.GetFileName(fileName));
        }

        transporter.CurrentFileChanged += transporter_CurrentFileChanged;
        transporter.CurrentProgressChanged += transporter_CurrentProgressChanged;
        transporter.TotalProgressChanged += transporter_TotalProgressChanged;
        transporter.CurrentWriteSpeedUpdated += transporter_CurrentWriteSpeedUpdated;
        transporter.TransportComplete += transporter_TransportComplete;

        transporter.BeginTransport();
    }

    void transporter_TransportComplete(FileTransportResult result)
    {
        Close();
    }

    void transporter_CurrentWriteSpeedUpdated(long bytesPerSecond)
    {
        double megaBytesPerSecond = (double)bytesPerSecond/1024000;

        currentSpeedLabel.SafeInvoke(x=> x.Text = string.Format("Transfer speed: {0:0.0} MB/s", megaBytesPerSecond));
    }

    private void transporter_TotalProgressChanged(int percentComplete)
    {
        totalProgressBar.SafeInvoke(x => x.Value = percentComplete);
    }

    private void transporter_CurrentProgressChanged(int percentComplete)
    {
        currentProgressBar.SafeInvoke(x => x.Value = percentComplete);
    }

    private void transporter_CurrentFileChanged(string fileName)
    {
        this.SafeInvoke(x => x.Text = string.Format("Current file: {0}", fileName));
    }
}

}

EDIT: SafeInvoke code added

public static void SafeInvoke<T>(this T @this, Action<T> action) where T : Control
    {
        if (@this.InvokeRequired)
        {
            @this.Invoke(action, new object[] {@this});
        }
        else
        {
            if (!@this.IsHandleCreated) return;

            if (@this.IsDisposed)
                throw new ObjectDisposedException("@this is disposed.");

            action(@this);
        }
    }

Answer 1

Well, if transporter_CurrentProgressChanged gets correct values, the program works properly. You can try to add some minimal Thread.Sleep call to InvokeCurrentProgressChanged (maybe with 0 parameter) when progress value is 100%, to get UI chance to update itself, but in this case you reduce the program performance. It is possibly better to leave the program unchanged, since it works as expected, and main progress bar is updated.