c# - 请向我解释这个 BackgroundWorker 事件

Question

我正在试验 BackgroundWorker，并尝试根据事件通知我的主线程。这些东西对我来说都是新的，想问一下，我做的好不好。

我简化了我的一个 winforms 问题，通过以下方式:(它只有 1 个按钮，当我按下它时在另一个线程中计数到 10)

public partial class Form1 : Form
{
    public void Subscribe(CountToTen c)
    {
        c.HandleWorkerEvent += new CountToTen.WorkerHandler(OtherThreadFinished);
    }
    private void OtherThreadFinished(CountToTen c, EventArgs e)
    {
        Debug.WriteLine("I'm ready !!!");
    }

    public Form1()
    {
        InitializeComponent();
    }

    private void btn_do_Click(object sender, EventArgs e)
    {
        CountToTen newThread = new CountToTen();
        Subscribe(newThread);
        newThread.StartCountingAndReportIfFinished();
    }
}

CountToTen 类:

public class CountToTen
{

    public event WorkerHandler HandleWorkerEvent;
    public EventArgs e;
    public delegate void WorkerHandler(CountToTen c, EventArgs e);
    public void StartCountingAndReportIfFinished()
    {
        BackgroundWorker worker = new BackgroundWorker();

        worker.DoWork += delegate(object s, DoWorkEventArgs args)
        {
            for (int i = 1; i <= 10; i++)
            {
                Thread.Sleep(300);
                Debug.WriteLine("Counting :" + i.ToString());

            }
        };

        worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(delegate(object o, RunWorkerCompletedEventArgs args)
            {
                Debug.WriteLine("Fromt Thread2 : I am finished!");
                if (HandleWorkerEvent != null)
                {
                    HandleWorkerEvent(this, e);
                }
            });

        worker.RunWorkerAsync();
        worker.Dispose();
    }
}

我试图创建一个事件，当 BW 完成时，并在我的主窗体中订阅这个事件。它工作正常，但是，我真的不明白这一行发生了什么:

worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(delegate(object o, RunWorkerCompletedEventArgs args)
            {
                Debug.WriteLine("Fromt Thread2 : I am finished!");
                if (HandleWorkerEvent != null)
                {
                    HandleWorkerEvent(this, e);
                }
            });

我不是在这里为我的 BW 创建一个事件，当它完成时，然后为主线程调用另一个吗？这不是矫枉过正吗？我也可以直接订阅 RunWorkerCompleteEventHandler 吗？

这里有点糊涂，请初学者指教。谢谢

Answer 1

这是对 BackgroundWorker 的 RunWorkerCompleted 事件的订阅。您可以使用匿名方法或命名方法来执行此操作。您也可以通过这种方式删除委托(delegate)类型声明:

worker.RunWorkerCompleted += (o, args) => 
{
    // raise HandleWorkerEvent if there is any subscriber exists
    if (HandleWorkerEvent != null)    
        HandleWorkerEvent(this, e);

    worker.Dispose();
};

使用命名方法，这看起来像

worker.RunWorkerCompleted += Worker_RunWorkerCompleted;

处理程序:

void Worker_RunWorkerCompleted(object o, RunWorkerCompletedEventArgs args)
{
    if (HandleWorkerEvent != null)    
        HandleWorkerEvent(this, e);

    ((BackgroundWorker)o).Dispose();
}

顺便说一句，我认为上课比较好，它只有数到十的逻辑。在您的表单上创建 BackgroundWorker，并在 DoWork 事件处理程序中使用此类。此外，表单将处置其所有组件。