7

我们有一个 WPF 繁忙窗口指示器。它显示在主线程上，使用window.ShowDialog(). 在响应 Loaded 事件时，将执行一个操作并关闭窗口，以便应用程序继续其工作。

window.ShowDialog()似乎不时（非常罕见）挂起而不显示对话框，并且未触发 Loaded 事件，因此应用程序挂起。相关代码如下：

private void BusyIndicatorAsyncCall(string text, Action<DoWorkEventArgs> doWorkDinamicView = null, Action doWork = null, Action workCompleted = null, Action<Exception> exceptionReturn = null)
{
    Window window = this.CreateWindowOfBusyIndicator(text);
    Dispatcher dispatcher = window.Dispatcher;
    BackgroundWorker backgoundworker = new BackgroundWorker();
    IViewModel viewModel = (window.Content as UserControl).DataContext as IViewModel;

    this.Modals.Add(viewModel, window);
    if (doWorkDinamicView != null)
    {
        DoWorkEventArgs eventArgs = new DoWorkEventArgs(window.Content);
        backgoundworker.DoWork += (s, e) => doWorkDinamicView.Invoke(eventArgs);
    }
    else if (doWork != null)
    {
        backgoundworker.DoWork += (s, e) => { doWork.Invoke(); };
    }

    backgoundworker.RunWorkerCompleted += (s, e) =>
    {
        Exception exception = e.Error;
        if (exception == null)
        {
            if (workCompleted != null)
            {
                try
                {
                    this.StyleName = null;
                    workCompleted.Invoke();
                }
                catch (Exception ex)
                {
                    exception = ex;
                }
            }
        }
        this.Modals.Remove(viewModel);
        dispatcher.Invoke(new Action(window.Close));
        if (exception != null)
        {
            if (exceptionReturn == null)
                throw new Exception("Error en RunWorkerCompleted.", exception);
            else
                exceptionReturn(exception);
        }
    };

    RoutedEventHandler onLoaded = new RoutedEventHandler((sender, e) =>
                            {
                                try
                                {
                                    backgoundworker.RunWorkerAsync();
                                }
                                catch
                                {
                                }
                            });
    this.BusyIndicatorImpl(window, onLoaded);
}

private void BusyIndicatorImpl(Window window, RoutedEventHandler onLoaded)
{
    window.Loaded += onLoaded;
    window.ShowDialog();
    window.Loaded -= onLoaded;
}

当应用程序挂起时，我可以看到window.ShowDialog()方法上的指令指针，但窗口在应用程序上不可见，并且 backgroundWorker 尚未启动，所以我的猜测是 OnLoaded 事件尚未引发。

该应用程序并没有真正挂起，因为它正确重绘，但您无法单击屏幕上的任何位置。作为一个奇怪的副作用，当应用程序挂起时，它会从 Windows 7 的任务栏中消失。

我在中断执行时看到的调用堆栈如下：

user32.dll!_NtUserGetMessage@16()  + 0x15 bytes 
user32.dll!_NtUserGetMessage@16()  + 0x15 bytes 
[Managed to Native Transition]  
WindowsBase.dll!MS.Win32.UnsafeNativeMethods.GetMessageW(ref System.Windows.Interop.MSG msg, System.Runtime.InteropServices.HandleRef hWnd, int uMsgFilterMin, int uMsgFilterMax) + 0x14 bytes  
WindowsBase.dll!System.Windows.Threading.Dispatcher.GetMessage(ref System.Windows.Interop.MSG msg, System.IntPtr hwnd, int minMessage, int maxMessage) + 0x80 bytes 
WindowsBase.dll!System.Windows.Threading.Dispatcher.PushFrameImpl(System.Windows.Threading.DispatcherFrame frame) + 0x75 bytes        WindowsBase.dll!System.Windows.Threading.Dispatcher.PushFrame(System.Windows.Threading.DispatcherFrame frame) + 0x49 bytes    
PresentationFramework.dll!System.Windows.Window.ShowHelper(object booleanBox) + 0x17d bytes 
PresentationFramework.dll!System.Windows.Window.Show() + 0x5c bytes 
PresentationFramework.dll!System.Windows.Window.ShowDialog() + 0x27d bytes  
>   xxx.dll!xxx.BusyIndicatorImpl(System.Windows.Window window, System.Windows.RoutedEventHandler onLoaded) Line 743 + 0xd bytes    C#

正如其他人之前所说的那样，它看起来像一个死锁，所以我使用 Visual Studio 进行了转储，并在其上运行了一些工具来寻找死锁。这是应用程序正在运行的线程的信息：

Debugger Thread ID  Managed Thread ID   OS Thread ID    Thread Object   GC Mode     Domain  Lock Count  Apt Exception
0                   1                   5684            2b2390          Preemptive  9176600 0           STA  
6                   2                   5572            2c7a80          Preemptive  2a82f8  0           MTA (Finalizer) 
7                   3                   3676            2cb828          Preemptive  2a82f8  0           Unknown  
11                  4                   864             7f7d5c0         Preemptive  2a82f8  0           MTA (Threadpool Worker) 
15                  10                  4340            921cdc8         Preemptive  9176600 1           MTA  
16                  12                  1648            9438560         Preemptive  2a82f8  0           MTA (Threadpool Completion Port) 
17                  14                  3380            9001038         Preemptive  2a82f8  0           Unknown (Threadpool Worker) 
21                  7                   5336            9002fe8         Preemptive  2a82f8  0           MTA (Threadpool Worker) 
20                  5                   4120            9003fc0         Preemptive  2a82f8  0           MTA (Threadpool Worker) 
25                  18                  5172            9004508         Preemptive  2a82f8  0           MTA (Threadpool Worker) 
27                  11                  5772            9003a78         Preemptive  2a82f8  0           MTA (Threadpool Worker)

应用程序代码只有一个线程（0，使用 ShowDialog 调用托管 1）。其他线程没有应用程序代码，线程 15（托管 10）是唯一有一些 .Net 代码的线程。

查看线程 15（托管 10），因为它是带锁的线程，我看到以下调用堆栈：

[[HelperMethodFrame_1OBJ] (System.Threading.WaitHandle.WaitMultiple)] System.Threading.WaitHandle.WaitMultiple(System.Threading.WaitHandle[], Int32, Boolean, Boolean) 
mscorlib_ni!System.Threading.WaitHandle.WaitAny(System.Threading.WaitHandle[], Int32, Boolean)+92 
System_ni!System.Net.TimerThread.ThreadProc()+28f 
mscorlib_ni!System.Threading.ThreadHelper.ThreadStart_Context(System.Object)+6f 
mscorlib_ni!System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)+a7 
mscorlib_ni!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)+16 
mscorlib_ni!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object)+41 
mscorlib_ni!System.Threading.ThreadHelper.ThreadStart()+44 
[[GCFrame]] 
[[DebuggerU2MCatchHandlerFrame]] 
[[ContextTransitionFrame]] 
[[DebuggerU2MCatchHandlerFrame]]

这个调用堆栈看起来像一个等待被解雇的计时器，但也许我对这种解释错了，所以我不知道如何继续。

我可以根据要求提供您需要的任何信息。我不是 WinDbg 方面的专家，但我开始能够处理它，因此您也可以要求我获取有关它的信息。

更新 ：

将一些日志添加到应用程序后，我们有以下额外信息：

问题是该方法dispatcher.Invoke(new Action(window.Close));被调用并且它在没有抛出异常的情况下执行但该方法window.ShowDialog();没有返回。

我们试图用 Spy++ 和类似工具找到窗口，据我所知，窗口不存在，但window.ShowDialog();一直在执行。

我希望这能让您对正在发生的事情有所了解。

4

3 回答 3

3

I found the cause of the issue one year latter, the following code shows a proof of concept of what is happening:

Summarizing (due to a race condition in the real code) there are 3 windows with a parent - child relation (A-->B-->C) and the code is closing B. This works on a WPF application (and C gets closed too) but in a VSTO add-in does not work and hangs, B never leaves the ShowDialog method:

Create a new VSTO project for Office Word 2010 and paste the following code (not sure about what happens if you target a different Office version):

using System.Diagnostics;
using System.Windows;
using System.Windows.Interop;
using Action = System.Action;

namespace WordAddIn1HangTest
{
    public partial class ThisAddIn
    {
        private void ThisAddIn_Startup(object sender, System.EventArgs e)
        {
            Window window1 = new Window();
            window1.Content = "1";
            Window window2 = new Window();
            window2.Content = "2";
            WindowInteropHelper windowInteropHelper1 = new WindowInteropHelper(window1);
            WindowInteropHelper windowInteropHelper2 = new WindowInteropHelper(window2);

            System.Windows.Threading.Dispatcher.CurrentDispatcher.BeginInvoke(new Action(() =>
            {
                windowInteropHelper1.Owner = Process.GetCurrentProcess().MainWindowHandle;
                window1.ShowDialog();
                MessageBox.Show("Hello");
            }));

            System.Windows.Threading.Dispatcher.CurrentDispatcher.BeginInvoke(new Action(() =>
            {
                windowInteropHelper2.Owner = windowInteropHelper1.Handle;
                window2.ShowDialog();
            }));

            System.Windows.Threading.Dispatcher.CurrentDispatcher.BeginInvoke(new Action(() =>
            {
                window1.Close();
            }));
        }

        private void ThisAddIn_Shutdown(object sender, System.EventArgs e)
        {
        }

        #region VSTO generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InternalStartup()
        {
            this.Startup += new System.EventHandler(ThisAddIn_Startup);
            this.Shutdown += new System.EventHandler(ThisAddIn_Shutdown);
        }

        #endregion
    }
}

As the window1 gets closed you should expect to see the message "Hello". Instead of that you don't see any window open and the ShowDialog call gets hang.

于 2018-01-11T13:54:01.150 回答
1

可能是死锁，但我们没有足够的信息来开始（例如，Loaded事件处理程序内部发生了什么，或者在什么上下文中调用了事物）。

您的代码有一些值得仔细研究的地方：

  • 您似乎没有设置模式对话框的所有者。在最坏的情况下，这可能会导致您的模态对话框显示在背景中，这可能很难或不可能关闭。

  • 目前尚不清楚您在哪里创建窗口。该Loaded事件只会在您的窗口第一次显示时触发（与例如Activated事件相反）。如果您回收窗口，则不会触发加载的事件，并且不会启动您的后台工作程序。

这是一个非常基本的工作 WPF 示例，包括一个带有后台工作人员的主窗口和一个模式进度对话框。我会尝试从这里开始尝试隔离问题。

主窗口.xaml

<Window x:Class="ProgressBarSample.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        Title="MainWindow"
        Width="200"
        Height="100"
        mc:Ignorable="d">
    <Grid>
        <Button Click="OnButtonClick">Start</Button>
    </Grid>
</Window>

主窗口.xaml.cs

using System.ComponentModel;
using System.Threading;
using System.Windows;

namespace ProgressBarSample
{
    public partial class MainWindow
    {
        private BackgroundWorker _backgroundWorker;
        private ProgressWindow _progressWindow;

        public MainWindow()
        {
            InitializeComponent();
        }

        private void OnButtonClick(object sender, RoutedEventArgs e)
        {
            _progressWindow = new ProgressWindow { Owner = this };
            _backgroundWorker = new BackgroundWorker { WorkerReportsProgress = true };
            _backgroundWorker.DoWork += OnWorkerDoWork;
            _backgroundWorker.RunWorkerCompleted += OnWorkerRunWorkerCompleted;
            _backgroundWorker.ProgressChanged += OnWorkerProgressChanged;
            _backgroundWorker.RunWorkerAsync();
            _progressWindow.ShowDialog();
        }

        private void OnWorkerProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            _progressWindow.ProgressValue = e.ProgressPercentage;
        }

        private void OnWorkerRunWorkerCompleted(
            object sender, 
            RunWorkerCompletedEventArgs e)
        {
            _progressWindow.Close();
            MessageBox.Show("Done");
        }

        private void OnWorkerDoWork(object sender, DoWorkEventArgs e)
        {
            int initialValue = 100;
            for (int i = 0; i < initialValue; i++)
            {
                Thread.Sleep(50);
                _backgroundWorker.ReportProgress(i);
            }
        }
    }
}

进度窗口.xaml

<Window x:Class="ProgressBarSample.ProgressWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        Title="Progress"
        Width="300"
        Height="100"
        mc:Ignorable="d">
    <Grid>
        <ProgressBar Maximum="100" Minimum="0"
                     Value="{Binding ProgressValue}" />
    </Grid>
</Window>

ProgressWindow.xaml.cs

using System.ComponentModel;
using System.Runtime.CompilerServices;

namespace ProgressBarSample
{
    public partial class ProgressWindow : INotifyPropertyChanged
    {
        private double _progressValue;

        public ProgressWindow()
        {
            InitializeComponent();
            DataContext = this;
        }

        public double ProgressValue
        {
            get { return _progressValue; }
            set
            {
                _progressValue = value;
                OnPropertyChanged();
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;

        protected virtual void OnPropertyChanged(
            [CallerMemberName] string propertyName = null)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}
于 2016-11-22T09:36:37.453 回答
0

调用堆栈显示您的对话框处于模式消息循环中等待消息。它没有被锁定或阻止。

正如 Dirk 指出的那样，Loaded 事件并不总是被引发。其来源可能是他建议的两件事之一。

一种解决方法是在 BusyIndi​​catorImpl 中显式调用 onLoaded。

private void BusyIndicatorImpl(Window window, RoutedEventHandler onLoaded)
{
    onLoaded();
    window.ShowDialog();
}

或者，您可以将其发布到您的模态对话框中。

private void BusyIndicatorImpl(Window window, RoutedEventHandler onLoaded)
{
    window.Dispatcher.InvokeAsync(() => onLoaded(window, null));
    window.ShowDialog();
}
于 2016-11-28T15:26:40.097 回答