CancelAsync 是否有效？

发布于 2024-11-02 05:17:40 字数 1274 浏览 0 评论 0原文

我制作了一个小型应用程序，其中 Form 是线程化的（使用 BackgroundWorker），并在表单中调用 QuitApplication 中的函数 QuitApplication当我想退出时，使用 code>Program 类。

DoWork 看起来像这样：

static void guiThread_DoWork(object sender, DoWorkEventArgs e)
{
    BackgroundWorker worker = sender as BackgroundWorker;

    while (true)
    {
        if (worker.CancellationPending == true)
        {
            e.Cancel = true;
            break;
        }

        if (Program.instance.form != null)
        {
            Program.instance.form.UpdateStatus(Program.instance.statusText, Program.instance.statusProgress);
        }

        Thread.Sleep(GUI_THREAD_UPDATE_TIME);
    }
}

在 Form1 类中，我将此方法附加到关闭窗口：

void Form1_FormClosed(object sender, FormClosedEventArgs e)
{
    Program.instance.SetStatus("Closing down...", 0);

    Program.QuitApplication();
}

所以我想要的是确保当我按窗口上的 X 时，一切都会退出。然而，if(worker.CancellationPending == true)从未命中……这是为什么？

QuitApplication 看起来像这样：

public static void QuitApplication()
{
    Program.instance.guiThread.CancelAsync();

    Application.Exit();
}

我使用 guiThread.WorkerSupportsCancellation = true

原文

I've made a small app where Form is threaded (using BackgroundWorker), and in the form I'm calling a function QuitApplication in Program class when I want to quit.

The DoWork looks like this:

static void guiThread_DoWork(object sender, DoWorkEventArgs e)
{
    BackgroundWorker worker = sender as BackgroundWorker;

    while (true)
    {
        if (worker.CancellationPending == true)
        {
            e.Cancel = true;
            break;
        }

        if (Program.instance.form != null)
        {
            Program.instance.form.UpdateStatus(Program.instance.statusText, Program.instance.statusProgress);
        }

        Thread.Sleep(GUI_THREAD_UPDATE_TIME);
    }
}

and in the Form1 class i have this method attached to the closing of the window:

void Form1_FormClosed(object sender, FormClosedEventArgs e)
{
    Program.instance.SetStatus("Closing down...", 0);

    Program.QuitApplication();
}

So what i want is to ensure that everything quits when I press the X on the window. However, the if( worker.CancellationPending == true ) never hits... why is this?

QuitApplication looks like this:

public static void QuitApplication()
{
    Program.instance.guiThread.CancelAsync();

    Application.Exit();
}

And Im using guiThread.WorkerSupportsCancellation = true

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怎樣才叫好 2024-11-09 05:17:40

CancelAsync 正在设置 CancellationPending 属性，但随后您立即退出应用程序，而没有让后台线程有机会检测到并关闭。您需要更改 UI 代码以等待后台线程完成。

就我个人而言，当我编写这样的应用程序时，我使表单关闭按钮充当取消按钮，而不是立即退出。对于最终用户来说更安全。例如：

private void abortButton_Click(object sender, EventArgs e) {
    // I would normally prompt the user here for safety.
    worker.CancelAsync();
}

private void Form1_FormClosing(object sender, FormClosingEventArgs e) {
    if(worker.IsBusy) {
        // If we are still processing, it's not very friendly to suddenly abort without warning.
        // Convert it into a polite request instead.
        abortButton.PerformClick();
        e.Cancel = true;
    }
}

CancelAsync is setting the CancellationPending property, but then you immediately quit the application without giving the background thread a chance to detect that and shut down. You need to change your UI code to wait for the background thread to finish.

Personally, when I write apps like this, I make the form close button act like a Cancel button rather than quit immediately. It's a lot safer for the end user. For example:

private void abortButton_Click(object sender, EventArgs e) {
    // I would normally prompt the user here for safety.
    worker.CancelAsync();
}

private void Form1_FormClosing(object sender, FormClosingEventArgs e) {
    if(worker.IsBusy) {
        // If we are still processing, it's not very friendly to suddenly abort without warning.
        // Convert it into a polite request instead.
        abortButton.PerformClick();
        e.Cancel = true;
    }
}

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