wpf - 如果出现“必须在附加到新父 Visual 之前必须从当前父 Visual 断开指定子视觉”异常，如何调试视觉树

Question

您如何调试以下错误？

在附加到新的父 Visual 之前，必须断开指定子与当前父 Visual 的连接。

我确定我理解了这个的意思，Exception但如果我错过了一些重要的事情，我认为这意味着：

一个基于的对象FrameworkElement确实已经存在于可视树中的某个地方，我正试图将它再次添加到树中的其他地方。

要解决这个问题，我有 2 个选项：

将其从视觉树中的当前位置删除，或
根据我的实现克隆它。

到目前为止一切顺利，但为什么这Exception不能告诉我需要修改什么类型的孩子？因为如果您尝试使用的对象包含多个子对象，您必须在每个类中查找才能找到抛出 this 的对象Exception。

有没有简单的方法可以找到对象？我认为堆栈跟踪并不是很有帮助。

这里是堆栈跟踪：

UnhandledException=System.ArgumentException: Must disconnect specified child from current parent Visual before attaching to new parent Visual.
   at System.Windows.Media.Visual.AddVisualChild(Visual child)
   at MS.Internal.Documents.FlowDocumentView.ArrangeOverride(Size arrangeSize)
   at System.Windows.FrameworkElement.ArrangeCore(Rect finalRect)
   at System.Windows.UIElement.Arrange(Rect finalRect)
   at System.Windows.Controls.ScrollContentPresenter.ArrangeOverride(Size arrangeSize)
   at System.Windows.FrameworkElement.ArrangeCore(Rect finalRect)
   at System.Windows.UIElement.Arrange(Rect finalRect)
   at System.Windows.Controls.Grid.ArrangeOverride(Size arrangeSize)
   at System.Windows.FrameworkElement.ArrangeCore(Rect finalRect)
   at System.Windows.UIElement.Arrange(Rect finalRect)
   at System.Windows.Controls.Control.ArrangeOverride(Size arrangeBounds)
   at System.Windows.Controls.ScrollViewer.ArrangeOverride(Size arrangeSize)
   at System.Windows.FrameworkElement.ArrangeCore(Rect finalRect)
   at System.Windows.UIElement.Arrange(Rect finalRect)
   at System.Windows.Controls.Border.ArrangeOverride(Size finalSize)
   at System.Windows.FrameworkElement.ArrangeCore(Rect finalRect)
   at System.Windows.UIElement.Arrange(Rect finalRect)
   at System.Windows.Controls.Grid.ArrangeOverride(Size arrangeSize)
   at System.Windows.FrameworkElement.ArrangeCore(Rect finalRect)
   at System.Windows.UIElement.Arrange(Rect finalRect)
   at System.Windows.Controls.Control.ArrangeOverride(Size arrangeBounds)
   at System.Windows.FrameworkElement.ArrangeCore(Rect finalRect)
   at System.Windows.UIElement.Arrange(Rect finalRect)
   at System.Windows.Controls.StackPanel.StackArrangeHelper(IStackMeasure arrangeElement, IStackMeasureScrollData scrollData, Size arrangeSize)
   at System.Windows.Controls.StackPanel.ArrangeOverride(Size arrangeSize)
   at System.Windows.FrameworkElement.ArrangeCore(Rect finalRect)
   at System.Windows.UIElement.Arrange(Rect finalRect)
   at MS.Internal.Helper.ArrangeElementWithSingleChild(UIElement element, Size arrangeSize)
   at System.Windows.Controls.ContentPresenter.ArrangeOverride(Size arrangeSize)
   at System.Windows.FrameworkElement.ArrangeCore(Rect finalRect)
   at System.Windows.UIElement.Arrange(Rect finalRect)
   at System.Windows.Controls.Border.ArrangeOverride(Size finalSize)
   at System.Windows.FrameworkElement.ArrangeCore(Rect finalRect)
   at System.Windows.UIElement.Arrange(Rect finalRect)
   at System.Windows.Controls.Control.ArrangeOverride(Size arrangeBounds)
   at System.Windows.FrameworkElement.ArrangeCore(Rect finalRect)
   at System.Windows.UIElement.Arrange(Rect finalRect)
   at MS.Internal.Helper.ArrangeElementWithSingleChild(UIElement element, Size arrangeSize)
   at System.Windows.Controls.ContentPresenter.ArrangeOverride(Size arrangeSize)
   at System.Windows.FrameworkElement.ArrangeCore(Rect finalRect)
   at System.Windows.UIElement.Arrange(Rect finalRect)
   at System.Windows.Controls.Border.ArrangeOverride(Size finalSize)
   at System.Windows.FrameworkElement.ArrangeCore(Rect finalRect)
   at System.Windows.UIElement.Arrange(Rect finalRect)
   at System.Windows.Controls.Control.ArrangeOverride(Size arrangeBounds)
   at System.Windows.Controls.DataGridCell.ArrangeOverride(Size arrangeSize)
   at System.Windows.FrameworkElement.ArrangeCore(Rect finalRect)
   at System.Windows.UIElement.Arrange(Rect finalRect)
   at System.Windows.Controls.Grid.ArrangeOverride(Size arrangeSize)
   at System.Windows.FrameworkElement.ArrangeCore(Rect finalRect)
   at System.Windows.UIElement.Arrange(Rect finalRect)
   at System.Windows.ContextLayoutManager.UpdateLayout()
   at System.Windows.UIElement.UpdateLayout()
   at System.Windows.Interop.HwndSource.SetLayoutSize()
   at System.Windows.Interop.HwndSource.set_RootVisualInternal(Visual value)
   at System.Windows.Interop.HwndSource.set_RootVisual(Visual value)
   at System.Windows.Window.SetRootVisual()
   at System.Windows.Window.SetRootVisualAndUpdateSTC()
   at System.Windows.Window.SetupInitialState(Double requestedTop, Double requestedLeft, Double requestedWidth, Double requestedHeight)
   at System.Windows.Window.CreateSourceWindow(Boolean duringShow)
   at System.Windows.Window.CreateSourceWindowDuringShow()
   at System.Windows.Window.SafeCreateWindowDuringShow()
   at System.Windows.Window.ShowHelper(Object booleanBox)
   at System.Windows.Window.Show()
   at System.Windows.Window.ShowDialog()
   at Speiseplandienst.ViewModels.BestellscheinUebersichtListVM.OnEdit() in C:\_\_\_\_\_\_\_\BestellscheinUebersichtListVM.cs:Line 30.
   at Framework.ListVM.Edit() in C:\_\_\_\_\_\_\Controls\ListVM.cs:Line 118.
   at Framework.ListVM.<get_EditCommand>b__8(Object param) in C:\_\_\_\_\_\_\Controls\ListVM.cs:Line 101.
   at Framework.RelayCommand.Execute(Object parameter) in C:\_\_\_\Framework\Tools\RelayCommand.cs:Line 132.
   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 MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)
   at System.Windows.Threading.Dispatcher.LegacyInvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs)
   at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
   at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg)
   at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame)
   at System.Windows.Threading.Dispatcher.PushFrame(DispatcherFrame frame)
   at System.Windows.Threading.Dispatcher.Run()
   at System.Windows.Application.RunDispatcher(Object ignore)
   at System.Windows.Application.RunInternal(Window window)
   at System.Windows.Application.Run(Window window)
   at System.Windows.Application.Run()
   at Speiseplandienst.MainRun.Main(String[] args) in C:\_\_\_\_\_\_\Main.cs:Line 18.

score 1 · Accepted Answer

此错误可能有许多不同的原因。例如，如果您Visual多次尝试将同一对象添加到 UI 集合控件中，则会发生此错误。如果您尝试将所选项目（UI 对象）从一个ListBox添加到另一个（而不仅仅是添加数据），您将收到此错误。如果您尝试将一个Image对象设置为另一个Image已经在 UI 中的对象，而不是将的Source属性设置Image为 current的属性Image，您将收到此错误。

如果没有看到您的代码，我们将无法弄清楚您为什么会收到此错误...从您的堆栈跟踪中，我猜您在ShowDialog()被调用时会收到此错误，但是除了那个之外没有太多线索问题可能出在该对话框或视图中。

希望现在您对问题有了更好的了解，您可以自己解决问题。

score 0 · Accepted Answer

我有一个类似的错误，因为在我使用 WPF 控件之前，我有另一个（不同的）对象与它交互。这是我需要删除的一些旧代码。我的例外信息是相似的The root Visual of a VisualTarget cannot have a parent...... 确保控件只使用一次。就我而言，我将 WPF 控件放在 Winforms 中ElementHost，然后尝试在 WPF 主机中使用它。

wpf - 如果出现“必须在附加到新父 Visual 之前必须从当前父 Visual 断开指定子视觉”异常，如何调试视觉树

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