我遇到了一个让我的应用程序崩溃的问题，我无法弄清楚原因。
我的代码是这样的：
Private Sub SelectedFieldFK_TextChanged() Handles SelectedFieldFK.TextChanged
RefreshSelections()
End Sub
Private Sub RefreshSelections()
If Selections Is Nothing Then Exit Sub
Selections.SetBinding(DataGrid.ItemsSourceProperty, New Binding With {.XPath = "..."})
m_SelectionSorter.Refresh()
If Selections.HasItems Then Selections.SelectedIndex = 0 '*)
End Sub
我正在使用箭头键跳过ListBox。通过绑定“SelectedFieldFK”不断更改其值，名为“Selections”的DataGrid不断更新。之后，选择DataGrid的第一行。当要显示2个选项时，这适用于第一次出现。然后我继续按下向下箭头，最终落在有一个选择的项目上。一旦函数“RefreshSelctions（）”结束，应用程序就崩溃了：
System.InvalidOperationException：只能在多种选择模式下更改SelectedItems集合。在单选模式下使用SelectedItem。
和StackTrace
at System.Windows.Controls.Primitives.Selector.OnSelectedItemsCollectionChanged(Object sender, NotifyCollectionChangedEventArgs e)
at System.Collections.ObjectModel.ObservableCollection`1.OnCollectionChanged(NotifyCollectionChangedEventArgs e)
at System.Collections.ObjectModel.ObservableCollection`1.InsertItem(Int32 index, T item)
at System.Windows.Controls.SelectedItemCollection.InsertItem(Int32 index, Object item)
at System.Collections.ObjectModel.Collection`1.Add(T item)
at System.Collections.ObjectModel.Collection`1.System.Collections.IList.Add(Object value)
at System.Windows.Controls.Primitives.Selector.UpdateSelectedItems(InternalSelectedItemsStorage toAdd, InternalSelectedItemsStorage toRemove)
at System.Windows.Controls.Primitives.Selector.UpdateSelectedItems()
at System.Windows.Controls.Primitives.Selector.UpdatePublicSelectionProperties()
at System.Windows.Controls.Primitives.Selector.SelectionChanger.End()
at System.Windows.Controls.Primitives.Selector.SelectionChanger.SelectJustThisItem(ItemInfo info, Boolean assumeInItemsCollection)
at System.Windows.Controls.ListBox.MakeSingleSelection(ListBoxItem listItem)
at System.Windows.Controls.ListBox.MakeKeyboardSelection(ListBoxItem item)
at System.Windows.Controls.ListBox.OnGotKeyboardFocus(Object sender, KeyboardFocusChangedEventArgs e)
at System.Windows.Input.KeyboardFocusChangedEventArgs.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.KeyboardDevice.ChangeFocus(DependencyObject focus, Int32 timestamp)
at System.Windows.Input.KeyboardDevice.TryChangeFocus(DependencyObject newFocus, IKeyboardInputProvider keyboardInputProvider, Boolean askOld, Boolean askNew, Boolean forceToNullIfFailed)
at System.Windows.Input.KeyboardDevice.Focus(DependencyObject focus, Boolean askOld, Boolean askNew, Boolean forceToNullIfFailed)
at System.Windows.Input.KeyboardDevice.Focus(IInputElement element)
at System.Windows.UIElement.Focus()
at System.Windows.Controls.ItemsControl.FocusItem(ItemInfo info, ItemNavigateArgs itemNavigateArgs)
at System.Windows.Controls.ListBox.FocusItem(ItemInfo info, ItemNavigateArgs itemNavigateArgs)
at System.Windows.Controls.ItemsControl.NavigateByLineInternal(Object startingItem, FocusNavigationDirection direction, FrameworkElement startingElement, ItemNavigateArgs itemNavigateArgs, Boolean shouldFocus, FrameworkElement& container)
at System.Windows.Controls.ItemsControl.NavigateByLine(ItemInfo startingInfo, FrameworkElement startingElement, FocusNavigationDirection direction, ItemNavigateArgs itemNavigateArgs)
at System.Windows.Controls.ItemsControl.NavigateByLine(FocusNavigationDirection direction, ItemNavigateArgs itemNavigateArgs)
at System.Windows.Controls.ListBox.OnKeyDown(KeyEventArgs e)
at System.Windows.UIElement.OnKeyDownThunk(Object sender, KeyEventArgs e)
at System.Windows.Input.KeyEventArgs.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.HwndKeyboardInputProvider.ReportInput(IntPtr hwnd, InputMode mode, Int32 timestamp, RawKeyboardActions actions, Int32 scanCode, Boolean isExtendedKey, Boolean isSystemKey, Int32 virtualKey)
at System.Windows.Interop.HwndKeyboardInputProvider.ProcessKeyAction(MSG& msg, Boolean& handled)
at System.Windows.Interop.HwndSource.CriticalTranslateAccelerator(MSG& msg, ModifierKeys modifiers)
at System.Windows.Interop.HwndSource.OnPreprocessMessage(Object param)
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 System.Windows.Threading.Dispatcher.Invoke(DispatcherPriority priority, Delegate method, Object arg)
at System.Windows.Interop.HwndSource.OnPreprocessMessageThunk(MSG& msg, Boolean& handled)
at System.Windows.Interop.HwndSource.WeakEventPreprocessMessage.OnPreprocessMessage(MSG& msg, Boolean& handled)
at System.Windows.Interop.ComponentDispatcherThread.RaiseThreadMessage(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 DatenfKatCreator.Application.Main() in C:\Users\Christoph\Documents\Visual Studio 2010\Projects\DatenfKatCreator\DatenfKatCreator\obj\x86\Debug\Resource\XAML\Application.g.vb:Zeile 66.
at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()
当我对行*)进行评论时，它可以正常工作，但当然没有选择第一个条目。
我错过了什么吗？
答案 0 :(得分：1)
您需要在网格上将属性SelectionMode设置为Extended
grid.SelectionMode = DataGridSelectionMode.Extended;
但是这应该是默认值，因此请检查您的代码（或XAML）是否将其更改为Single