c# - 检查 Dispatcher.CurrentDispatcher.Thread.ManagedThreadId 后的 CollectionView NotSupportedException

Question

我正在尝试使用 Task.Factory.StartNew() 运行后台操作。部分后台操作更新保存在 ObservableCollection 中的对象。我正在使用从 ObservableCollection 派生的自定义类来触发 OnCollectionChanged() 当集合中的一个对象的属性发生更改时(请参阅 https://stackoverflow.com/a/5256827/62072 )。如果有 CollectionView 绑定(bind)到 ObservableCollection，那么我会得到一个异常:

System.NotSupportedException: This type of CollectionView does not support changes to its SourceCollection from a thread different from the Dispatcher thread.

我试图避免此异常，因此我添加了一些代码，以便仅在 UI 线程上运行时才触发 OnCollectionChanged()。但不知何故我仍然得到异常(exception)..

这是我的 ItemPropertyChanged() 方法:

void ItemPropertyChanged(object sender, PropertyChangedEventArgs e)
{
    var a = new NotifyCollectionChangedEventArgs(
        NotifyCollectionChangedAction.Reset);

    if (Thread.CurrentThread.ManagedThreadId
         == Dispatcher.CurrentDispatcher.Thread.ManagedThreadId)
    {
        OnCollectionChanged(a);
    }
}

这里是完整的异常(exception):

System.AggregateException was unhandled
  Message=A Task's exception(s) were not observed either by Waiting on the Task or accessing its Exception property. As a result, the unobserved exception was rethrown by the finalizer thread.
  Source=mscorlib
  StackTrace:
       at System.Threading.Tasks.TaskExceptionHolder.Finalize()
       Message=This type of CollectionView does not support changes to its SourceCollection from a thread different from the Dispatcher thread.
      InnerException: System.NotSupportedException
           Source=PresentationFramework
           StackTrace:
                at System.Windows.Data.CollectionView.OnCollectionChanged(Object sender, NotifyCollectionChangedEventArgs args)
                at System.Collections.Specialized.NotifyCollectionChangedEventHandler.Invoke(Object sender, NotifyCollectionChangedEventArgs e)
                at System.Collections.ObjectModel.ObservableCollection`1.OnCollectionChanged(NotifyCollectionChangedEventArgs e)
                at SourceLog.Model.TrulyObservableCollection`1.ItemPropertyChanged(Object sender, PropertyChangedEventArgs e) in C:\github.com\tomhunter-gh\SourceLog\SourceLog.Model\TrulyObservableCollection.cs:line 41
                at System.ComponentModel.PropertyChangedEventHandler.Invoke(Object sender, PropertyChangedEventArgs e)
                at SourceLog.Model.LogEntry.OnPropertyChanged(String property) in C:\github.com\tomhunter-gh\SourceLog\SourceLog.Model\LogEntry.cs:line 44
                at SourceLog.Model.LogEntry.set_Read(Boolean value) in C:\github.com\tomhunter-gh\SourceLog\SourceLog.Model\LogEntry.cs:line 28
                at SourceLog.Model.LogEntry.<MarkAsReadAndSave>b__0() in C:\github.com\tomhunter-gh\SourceLog\SourceLog.Model\LogEntry.cs:line 53
                at System.Threading.Tasks.Task.InnerInvoke()
                at System.Threading.Tasks.Task.Execute()
           InnerException: 

为什么异常会提示我不在 Dispatcher 线程上，而我已明确检查过我在 Dispatcher 线程上？

Answer 1

Dispatcher.CurrentDispatcher 与 UI 线程无关，正如该属性的名称所暗示的那样，它为您提供了当前线程的调度程序。因此，您创建了一个始终返回 true 的检查。使用 Application.Current.Dispatcher，也可以在所述调度程序上调用它而不是忽略更改。