當我將「SelectedIndex = 0」分配給DataGrid時，爲什麼會收到System.InvalidOperationException？

Question

我有一個問題，讓我的應用程序崩潰，我無法弄清楚爲什麼。

我的代碼是這樣的：

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，蹦蹦跳跳地走使用箭頭鍵列表框。通過綁定「SelectedFieldFK」不斷更改其值，並且名爲「Selections」的DataGrid不斷更新。之後，選擇DataGrid的第一行。這適用於第一次出現時要顯示2個選擇。然後我繼續按下向下的箭頭並最終落在有一個選擇的項目上。一旦函數「RefreshSelctions（）」結束，該應用程序崩潰：

System.InvalidOperationException：只能在多種選擇模式下更改SelectedItems集合。在單選模式下使用SelectedItem。

和堆棧跟蹤

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() 

當我註釋行*)出來，它的工作原理，但當然沒有選擇第一項。

我錯過了什麼嗎？

Answer 1

您需要設置該屬性的SelectionMode以擴展在網格

grid.SelectionMode = DataGridSelectionMode.Extended; 

不過，這應該是默認的，所以檢查你的代碼（或XAML）它更改爲單