.NET暂停调度程序处理时无法执行此操作

Question

我在实现System.ComponentModel.INotifyPropertyChanged的基类中有以下方法:

protected virtual void RaisePropertyChangedEventSynchronous(string propertyName)
{                    
    try
    {
        if (PropertyChanged != null)
        {
            Delegate[] delegates = this.PropertyChanged.GetInvocationList();
            foreach (PropertyChangedEventHandler handler in delegates)
            {                      
                try
                {
                    DispatcherObject dispatcherInvoker = handler.Target 
                        as DispatcherObject;
                    if (dispatcherInvoker != null)
                    {                                
                        dispatcherInvoker.Dispatcher.Invoke(DispatcherPriority.Normal, 
                            new Action(delegate
                        {
                            handler(this, new PropertyChangedEventArgs(propertyName));
                        }));
                    }
                    else
                    {
                        handler(this, new PropertyChangedEventArgs(propertyName));
                    }
                }
                catch (Exception ex)
                {                     
                    ExceptionPolicy.HandleException(ex, 
                        ExceptionHandlingPolicyNames.LogPolicy);
                }
            }
        }
    }
    catch (Exception ex)
    {
         ExceptionPolicy.HandleException(ex, ExceptionHandlingPolicyNames.LogPolicy);
    }
}

有时,我会将以下异常记录到文件中:

类型:System.InvalidOperationException,mscorlib,Version = 2.0.0.0,Culture = neutral,PublicKeyToken = b77a5c561934e089消息:暂停调度程序处理时无法执行此操作.来源:WindowsBase帮助链接:数据:System.Collections.ListDictionaryInternal TargetSite:Void PushFrame(System.Windows.Threading.DispatcherFrame)堆栈跟踪:位于System.Windows.Threading的System.Windows.Threading.Dispatcher.PushFrame(DispatcherFrame框架). System.Windows.Threading.Dispatcher.Invoke上的System.Windows.Threading.Dispatcher.InvokeImpl(DispatcherPriority优先级,TimeSpan超时,Delegate方法,Object args,Boolean isSingleParameter)中的DispatcherOperation.Wait(TimeSpan超时)(DispatcherPriority优先级,Delegate方法)在OCC600.Infrastructure.Dictionary.BusinessEntities.Observable.

如果我使用Dispatcher.BeginInvoke更新UI,我不会得到这些例外.但我发现使用BeginInvoke执行更新并不可靠,因为有时这些更改不会反映在用户界面上.

我该如何解决这个问题？

Answer 1

我假设您在后台线程上并且正在尝试在UI线程上引发PropertyChanged事件.我认为WPF为您处理线程更改; 你不应该这样做.

这是我写的一些代码.XAML:

<Window x:Class="WpfApplication2.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="350" Width="525">
  <Grid>
    <TextBlock Text="{Binding Value}" />
  </Grid>

C#:

public partial class MainWindow : Window {
  public MainWindow() {
    InitializeComponent();

    this.DataContext = new Backgrounder();
  }

  class Backgrounder : INotifyPropertyChanged {
    int value = 0;
    public Backgrounder() {
      ThreadPool.QueueUserWorkItem(o => {
        while (true) {
          this.value++;
          Notify("Value");
          Thread.Sleep(TimeSpan.FromSeconds(1));
        }
      });
    }

    public int Value { get { return this.value; } }

    public event PropertyChangedEventHandler PropertyChanged;

    void Notify(string property) {
      PropertyChangedEventHandler handler = PropertyChanged;
      if (handler != null) { 
        handler(this, new PropertyChangedEventArgs(property)); 
      }
    }
  }
}