Reassign ItemsSource - Items collection must be empty before using ItemsSource

I'm using ItemsSource on a ListView. I now want to perform a search and filter the items with an SQL query, so I reassign the ItemsSource; but then an exception is thrown: Items collection must be empty before using ItemsSource. Alright, but how can I empty the items collection? Items.Clear is not allowed when using ItemsSource..

Okay, code looks like this:

this.Songs.ItemsSource = this.Library.ExecuteQuery<Songs>("SELECT * FROM songs WHERE title LIKE '%" + search + "%' OR artist LIKE '%" + search + "%' OR album LIKE '%" + search + "%'");

This piece of code is executed every time the text in the search box is changed. Here are the exception details:

    System.InvalidOperationException was unhandled
  Message="Items collection must be empty before using ItemsSource."
  Source="PresentationFramework"
  StackTrace:
       bei System.Windows.Controls.ItemCollection.SetItemsSource(IEnumerable value)
       bei System.Windows.Controls.ItemsControl.OnItemsSourceChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
       bei System.Windows.DependencyObject.OnPropertyChanged(DependencyPropertyChangedEventArgs e)
       bei System.Windows.FrameworkElement.OnPropertyChanged(DependencyPropertyChangedEventArgs e)
       bei System.Windows.DependencyObject.NotifyPropertyChange(DependencyPropertyChangedEventArgs args)
       bei System.Windows.DependencyObject.UpdateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, Boolean coerceWithDeferredReference, OperationType operationType)
       bei System.Windows.DependencyObject.SetValueCommon(DependencyProperty dp, Object value, PropertyMetadata metadata, Boolean coerceWithDeferredReference, OperationType operationType, Boolean isInternal)
       bei System.Windows.DependencyObject.SetValue(DependencyProperty dp, Object value)
       bei System.Windows.Controls.ItemsControl.set_ItemsSource(IEnumerable value)
       bei Musiclibrary.Window1.Search_TextChanged(Object sender, TextChangedEventArgs e) in C:开发者_如何学Python\Dokumente und Einstellungen\v. Wurstemberger\Eigene Dateien\Visual Studio 2008\Projects\Musiclibrary\Musiclibrary\Window1.xaml.cs:Zeile 132.
       bei System.Windows.Controls.TextChangedEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
       bei System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
       bei System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
       bei System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
       bei System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
       bei System.Windows.UIElement.RaiseEvent(RoutedEventArgs e)
       bei System.Windows.Controls.Primitives.TextBoxBase.OnTextChanged(TextChangedEventArgs e)
       bei System.Windows.Controls.Primitives.TextBoxBase.OnTextContainerChanged(Object sender, TextContainerChangedEventArgs e)
       bei System.Windows.Controls.TextBox.OnTextContainerChanged(Object sender, TextContainerChangedEventArgs e)
       bei System.Windows.Documents.TextContainerChangedEventHandler.Invoke(Object sender, TextContainerChangedEventArgs e)
       bei System.Windows.Documents.TextContainer.EndChange(Boolean skipEvents)
       bei System.Windows.Documents.TextContainer.System.Windows.Documents.ITextContainer.EndChange(Boolean skipEvents)
       bei System.Windows.Documents.TextRangeBase.EndChange(ITextRange thisRange, Boolean disableScroll, Boolean skipEvents)
       bei System.Windows.Documents.TextRange.System.Windows.Documents.ITextRange.EndChange(Boolean disableScroll, Boolean skipEvents)
       bei System.Windows.Documents.TextRange.ChangeBlock.System.IDisposable.Dispose()
       bei System.Windows.Documents.TextEditorTyping.DoTextInput(TextEditor This, String textData, Boolean isInsertKeyToggled, Boolean acceptControlCharacters)
       bei System.Windows.Documents.TextEditorTyping.TextInputItem.Do()
       bei System.Windows.Documents.TextEditorTyping.ScheduleInput(TextEditor This, InputItem item)
       bei System.Windows.Documents.TextEditorTyping.OnTextInput(Object sender, TextCompositionEventArgs e)
       bei System.Windows.Controls.Primitives.TextBoxBase.OnTextInput(TextCompositionEventArgs e)
       bei System.Windows.UIElement.OnTextInputThunk(Object sender, TextCompositionEventArgs e)
       bei System.Windows.Input.TextCompositionEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
       bei System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
       bei System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
       bei System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
       bei System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
       bei System.Windows.UIElement.RaiseEvent(RoutedEventArgs args, Boolean trusted)
       bei System.Windows.Input.InputManager.ProcessStagingArea()
       bei System.Windows.Input.InputManager.ProcessInput(InputEventArgs input)
       bei System.Windows.Input.TextCompositionManager.UnsafeCompleteComposition(TextComposition composition)
       bei System.Windows.Input.TextCompositionManager.PostProcessInput(Object sender, ProcessInputEventArgs e)
       bei System.Windows.Input.InputManager.ProcessStagingArea()
       bei System.Windows.Input.InputManager.ProcessInput(InputEventArgs input)
       bei System.Windows.Input.TextCompositionManager.UnsafeStartComposition(TextComposition composition)
       bei System.Windows.Input.TextCompositionManager.PostProcessInput(Object sender, ProcessInputEventArgs e)
       bei System.Windows.Input.InputManager.ProcessStagingArea()
       bei System.Windows.Input.InputManager.ProcessInput(InputEventArgs input)
       bei System.Windows.Input.InputProviderSite.ReportInput(InputReport inputReport)
       bei System.Windows.Interop.HwndKeyboardInputProvider.ProcessTextInputAction(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
       bei System.Windows.Interop.HwndSource.OnPreprocessMessage(Object param)
       bei System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Boolean isSingleParameter)
       bei System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Boolean isSingleParameter, Delegate catchHandler)
       bei System.Windows.Threading.Dispatcher.WrappedInvoke(Delegate callback, Object args, Boolean isSingleParameter, Delegate catchHandler)
       bei System.Windows.Threading.Dispatcher.InvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Boolean isSingleParameter)
       bei System.Windows.Threading.Dispatcher.Invoke(DispatcherPriority priority, Delegate method, Object arg)
       bei System.Windows.Interop.HwndSource.OnPreprocessMessageThunk(MSG& msg, Boolean& handled)
       bei System.Windows.Interop.HwndSource.WeakEventPreprocessMessage.OnPreprocessMessage(MSG& msg, Boolean& handled)
       bei System.Windows.Interop.ComponentDispatcherThread.RaiseThreadMessage(MSG& msg)
       bei System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame)
       bei System.Windows.Threading.Dispatcher.PushFrame(DispatcherFrame frame)
       bei System.Windows.Threading.Dispatcher.Run()
       bei System.Windows.Application.RunDispatcher(Object ignore)
       bei System.Windows.Application.RunInternal(Window window)
       bei System.Windows.Application.Run(Window window)
       bei System.Windows.Application.Run()
       bei Musiclibrary.App.Main() in C:\Dokumente und Einstellungen\v. Wurstemberger\Eigene Dateien\Visual Studio 2008\Projects\Musiclibrary\Musiclibrary\obj\Debug\App.g.cs:Zeile 0.
       bei System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args)
       bei System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       bei Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       bei System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       bei System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       bei System.Threading.ThreadHelper.ThreadStart()
  InnerException: 

This is usually a sign that you're setting the ItemsSource property AND you have manipulated the actual elements within the ItemsControl itself meaning either you've put things in the XAML or have manually added Children to the ItemsControl.