在按钮单击事件中中止长时间运行的线程 [英] Abort long running thread in button click event

问题描述

在WPF应用程序中，我运行很长时间，该过程使用BlueBeam Q Server将文件转换为PDF.当该过程发生时，它不应冻结，因此编写了以下代码来解决该问题:

In my WPF application, I have a long running process which converts files to PDFs using BlueBeam Q Server. When the process takes place, it should not freeze, so the below code has written to take care of that:

private void btn_convert_Click(object sender, RoutedEventArgs e)
{
        thread = new Thread(new ThreadStart(WorkerMethod));
        thread.SetApartmentState(ApartmentState.STA);
        thread.IsBackground = true;
        thread.Name = "PDF";
        thread.Start();
}

WorkerMethod()
{
//code to connect to Q server and conversion goes here
}

现在，当过程开始时，取消按钮将对用户可见.当用户按下取消时，我想中止启动的线程.我写的代码如下:

Now, when the process starts, a cancel button will be visible to the user. When the user presses cancel, I want to abort the thread started. I wrote the code as below:

private void btn_cancel_Click(object sender, RoutedEventArgs e)
    {
        if (thread.Name == "PDF")
            thread.Abort(); 
    }

但是该线程不会中止并继续执行该过程.请给我您的宝贵建议.

But the thread doesn't abort and continues the process. Please give me your valuable suggestions.

推荐答案

您应尽可能避免使用Abort.在SO中搜索如何优雅地取消线程-当线程代码调用您无法影响的其他代码(例如第三方库方法或类似方法)时，将无法执行此操作.

You should avoid Abort whenever possible. Search SO for how to cancel threads gracefully - which can not be done when the thread code calls other code you can not influence, like a third party library method or something like that.

例如，如果您的线程方法执行以下操作:

For example if your thread method does something like this:

WorkerMethod()
{
    CallFunctionInExternalDLL();
}

无法正常终止.

要取消"该线程，最好指示该线程应取消(例如，使用bool标志)并使该线程回滚其结果(例如，删除创建的PDF或其他内容)像那样).然后，您的应用程序就可以继续运行，就好像从未启动线程一样.

To "cancel" such a thread, it's best to indicate to the thread it should cancel (using a bool flag, for example) and have the thread roll back its result (for example, delete a created PDF or things like that). Your application could then just continue as if the thread had never been started.

例如，您的代码可能如下所示:

For example your code could then look like this:

WorkerMethod()
{
    CallFunctionInExternalDLL();
    if (m_threadAborted)
        RollBackWhatFunctionDid();
}

如果您的线程如下所示:

If your thread looks like this:

WorkerMethod()
{
    while (true)
    {
        CallFunctionInExternalDLL();
    }
}

您可以这样做:

WorkerMethod()
{
    while (!m_threadAborted)
    {
        CallFunctionInExternalDLL();
    }

    if (m_threadAborted)
        RollBackStuff();
}

在这些示例中，m_threadAborted是这样声明的bool标志:

In these examples, m_threadAborted is a bool flag declared like this:

private volatile bool m_threadAborted = false;

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