句柄无效 - 取消令牌源

Question

曾几何时调用 CancellationTokenSource Cancel() 方法时出现异常：The handle is invalid.

   at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
   at System.Threading.EventWaitHandle.Set()
   at System.Threading.CancellationTokenSource.NotifyCancellation(Boolean throwOnFirstException)
   at System.Threading.CancellationTokenSource.Cancel()
   at .CancelProcess(Object obj) in proj\ViewModels\WorkflowContainerViewModel.cs:line 162
   at DelegateCommand.Execute(Object parameter) in proj\Commands\DelegateCommand.cs:line 32
   at MS.Internal.Commands.CommandHelpers.CriticalExecuteCommandSource(ICommandSource commandSource, Boolean userInitiated)
   at System.Windows.Controls.Primitives.ButtonBase.OnClick()
   at System.Windows.Controls.Button.OnClick()
   at System.Windows.Controls.Primitives.ButtonBase.OnMouseLeftButtonUp(MouseButtonEventArgs e)
   at System.Windows.UIElement.OnMouseLeftButtonUpThunk(Object sender, MouseButtonEventArgs e)
   at System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
   at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
   at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
   at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   at System.Windows.UIElement.ReRaiseEventAs(DependencyObject sender, RoutedEventArgs args, RoutedEvent newEvent)
   at System.Windows.UIElement.OnMouseUpThunk(Object sender, MouseButtonEventArgs e)
   at System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
   at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
   at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
   at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
   at System.Windows.UIElement.RaiseTrustedEvent(RoutedEventArgs args)
   at System.Windows.UIElement.RaiseEvent(RoutedEventArgs args, Boolean trusted)
   at System.Windows.Input.InputManager.ProcessStagingArea()
   at System.Windows.Input.InputManager.ProcessInput(InputEventArgs input)
   at System.Windows.Input.InputProviderSite.ReportInput(InputReport inputReport)
   at System.Windows.Interop.HwndMouseInputProvider.ReportInput(IntPtr hwnd, InputMode mode, Int32 timestamp, RawMouseActions actions, Int32 x, Int32 y, Int32 wheel)
   at System.Windows.Interop.HwndMouseInputProvider.FilterMessage(IntPtr hwnd, WindowMessage msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at System.Windows.Interop.HwndSource.InputFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)

我到处都找不到任何东西。有什么想法吗？

Answer 1

问题（正如在评论中指出的那样）是 CancellationToken 被序列化然后再次反序列化。

CancellationTokenSource（一个CancellationToken创建一个，如果你直接实例化它）持有一个非托管内核事件的引用（使用EventWaitHandle），并在内部持有一个引用到那个句柄。

当 CancellationTokenSource 被处置时，它会释放该非托管引用...所以如果您序列化令牌，它将使用该句柄序列化...之后，您就不会使用CancellationTokenSource 垃圾收集器收集它，并释放内核事件（因此句柄不再有效）。

现在在反序列化时，EventWaitHandle 取回值，但它不会再次创建内核事件（因为在反序列化时，您只是将值分配给字段，而不是通过构造再次逻辑），但它保留了旧的句柄......所以当你想取消它时，它会尝试使用一个不再有效的内核事件的句柄：因此，你的例外。

可能的解决方案：

不要 serialize/deserialize CancellationToken... 相反，在反序列化时构造一个不同的。
如果那不可能（因为你需要使用那个，不能使用其他），那么在某处保留 CancellationTokenSource 的引用，这样它就不会被垃圾收集，并且它从不释放内核事件，所以句柄在反序列化时仍然有效

句柄无效 - 取消令牌源

The handle is invalid - Cancellation token source

c#

cancellation