Question

如何将此类的CountValue更改报告给后台工作者

class SomeOtherClass
{
    public void CountUp()
    {
        int CountValue;
        for (int i = 0; i < 100000000; i++)
            CountValue = i;
    }
}

以下是DoWork功能的实现

   private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
    {
        BackgroundWorker worker = sender as BackgroundWorker;
        SomeOtherClass MyOtherClass = new SomeOtherClass();
        int CountValue;
        if ((worker.CancellationPending == true))
        {
            e.Cancel = true;
        }
        else
        {
            MyOtherClass.CountUp();
            worker.ReportProgress(CountValue);
        }
    }

Answer 1

现在看起来SomeOtherClass看起来并没有明显的方法。如果您可以更改SomeOtherClass，则可以添加一个事件：

class CountEventArgs : EventArgs
{
    public int CountValue { get; private set; }
    public CountEventArgs (int countValue)
    {
        CountValue = countValue;
    }
}
class SomeOtherClass
{
    public event EventHandler<CountEventArgs> CountValueChanged;
    public void CountUp()
    {
        int CountValue;
        for (int i = 0; i < 100000000; i++)
        {
            CountValue = i;
            OnCountValueChanged(new CountEventArgs(CountValue));
        }
    }
    private void OnCountValueChanged(CountEventArgs e)
    {
        EventHandler<CountEventArgs> temp = CountValueChanged;
        if (temp != null)
        {
            temp(this, e);
        }
    }
}

然后，您可以设置事件处理程序并使用BackgroundWorker的ReportProgress方法将信息中继到UI：

BackgroundWorker worker = sender as BackgroundWorker;
SomeOtherClass MyOtherClass = new SomeOtherClass();
// set up an anonymous method as event handler for the CountValueChanged
// event. This event handler passes the count value on to the ReportProgress
// method of the background worker, which in turn will raise the ProgressChanged
// event on the UI thread.
MyOtherClass.CountValueChanged += (eventSender, eventArgs) =>
{
    worker.ReportProgress(eventArgs.CountValue);
};

MyOtherClass.CountUp();

Answer 2

您的代码中出现了很多错误。特别是，当您每秒向其发送数百万次新事件时，您不能指望Windows能够跟上。尝试仅在完成大量工作后发送更新。此外，ReportProgress的参数应为百分比（0 - 100）。如果要发送百分比以外的数据，请使用用户状态参数。以下是您可以使用的一些代码：

using System;
using System.Windows.Forms;
using System.ComponentModel;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void btnStart_Click(object sender, EventArgs e)
        {
            backgroundWorker.RunWorkerAsync();
        }

        private void btnStop_Click(object sender, EventArgs e)
        {
            backgroundWorker.CancelAsync();
        }

        private void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
        {
            BackgroundWorker worker = (BackgroundWorker)sender;

            int countValue = 0;
            int max = 100000000;
            for (int i = 0; i < max; i++)
            {
                if (worker.CancellationPending)
                {
                    e.Cancel = true;
                    return;
                }

                countValue = i;
                if (i % 1000000 == 0)
                    worker.ReportProgress(i / (max / 100), i);
            }
            worker.ReportProgress(100, max);
        }

        private void backgroundWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            progressBar.Value = e.ProgressPercentage;
            labelCounter.Text = ((int)e.UserState).ToString();
        }
    }
}

注意：请记住在设计器中将worker的SupportsProgress和SupportsCancellation设置为true。

Answer 3

不确定我理解，但我会试一试。为什么不更改CountUp（）以返回值？

public int CountUp()    
{
    int CountValue;
    for (int i = 0; i < 100000000; i++)
        CountValue = i;    

    return CountValue;
}

这段代码的目的对我没有意义，所以我不确定我理解你想要完成什么。

Answer 4

我认为您不了解局部变量的工作原理... CountValue方法中的CountUp只会写入CountUp方法中的局部变量。它不会影响CountUp方法中的backgroundWorker_DoWork变量。您必须将CountUp移至DoWork方法才能生效。

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
    BackgroundWorker worker = sender as BackgroundWorker;
    for (int i = 0; i < 100000000; i++)
    {
        if (worker.CancellationPending)
        {
            e.Cancel = true;
            break;
        }

        worker.ReportProgress(i);
    }
}

如何使用远程类的backgroundworker

4 个答案: