Unable to cast object of type 'MS.Internal.NamedObject' to custom type

wpf casting prism observablecollection
Louis Kottmann picture Louis Kottmann · Nov 22, 2011 · Viewed 17.8k times · Source

I am not new to WPF, but I can't figure out this problem:

I use an ObservableCollection<MyCustomType> that i bind to ComboBoxes, it's all working great as usual, but at some point i need to change the content of the collection (i retrieve a new set from the database, that may or may not contain part of the old one).

Now adding or removing elements is all done by WPF, but if you change the whole collection I found you had to raise PropertyChanged for the collection.

The problem is that sometimes it crashes giving me a not-so-friendly exception.
I'm unsure of what exactly triggers the crash, but if I don't touch the View and retrieve a new set from DB, it doesn't crash.

Here is some code:

    public const string MyObsCollectionProperty = "MyObsCollection";
    private ObservableCollection<MyCustomType> m_MyObsCollection;
    public ObservableCollection<MyCustomType> MyObsCollection
    {
        get { return m_MyObsCollection; }
        set
        {
            m_MyObsCollection = value;
            RaisePropertyChanged(MyObsCollectionProperty); // <-- Crashes here
        }
    }

I get the exception: Unable to cast object of type 'MS.Internal.NamedObject' to type 'MyNameSpace.MyCustomType'

Please note that this exception comes from Prism, but it's probably just because i inherit from NotificationObject on my ViewModel.

I appreciate any help on this problem,

Regards,

LK.

EDIT: I think the problem comes from the ComboBox, and more specifically, from the way i set their properties.

I bind the ItemsSource property to an ObservableCollection, and to decide which element to select, I bind the SelectedValue to a field of an item of an ObservableCollection (the ComboBox is nested within a ListView).
I also set SelectedValuePath (you get the idea).

I guess when i change the first collection hell breaks lose on that setup. And it leaves it in peace when i don't touch the view because of virtualization (it is hidden at first).

ADDITION:

The InnerException is nulll.

Message: Unable to cast object of type 'MS.Internal.NamedObject' to type 'CocoonV4.DAL.WcfServiceCocoonV4.DekoTemplate'. 

   at Microsoft.Practices.Prism.Commands.DelegateCommand`1.<>c__DisplayClass6.<.ctor>b__3(Object o)
   at Microsoft.Practices.Prism.Commands.DelegateCommandBase.CanExecute(Object parameter)
   at Microsoft.Practices.Prism.Commands.DelegateCommandBase.System.Windows.Input.ICommand.CanExecute(Object parameter)
   at System.Windows.Interactivity.InvokeCommandAction.Invoke(Object parameter)
   at System.Windows.Interactivity.TriggerBase.InvokeActions(Object parameter)
   at System.Windows.Interactivity.EventTriggerBase.OnEvent(EventArgs eventArgs)
   at System.Windows.Interactivity.EventTriggerBase.OnEventImpl(Object sender, EventArgs eventArgs)
   at System.Windows.Controls.SelectionChangedEventArgs.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.RaiseEvent(RoutedEventArgs e)
   at System.Windows.Controls.ComboBox.OnSelectionChanged(SelectionChangedEventArgs e)
   at System.Windows.Controls.Primitives.Selector.InvokeSelectionChanged(List`1 unselectedItems, List`1 selectedItems)
   at System.Windows.Controls.Primitives.Selector.SelectionChanger.End()
   at System.Windows.Controls.Primitives.Selector.OnItemsChanged(NotifyCollectionChangedEventArgs e)
   at System.Windows.Controls.ItemsControl.OnItemCollectionChanged(Object sender, NotifyCollectionChangedEventArgs e)
   at System.Collections.Specialized.NotifyCollectionChangedEventHandler.Invoke(Object sender, NotifyCollectionChangedEventArgs e)
   at System.Windows.Data.CollectionView.OnCollectionChanged(NotifyCollectionChangedEventArgs args)
   at System.Windows.Controls.ItemCollection.System.Windows.IWeakEventListener.ReceiveWeakEvent(Type managerType, Object sender, EventArgs e)
   at System.Windows.WeakEventManager.DeliverEventToList(Object sender, EventArgs args, ListenerList list)
   at System.Windows.WeakEventManager.DeliverEvent(Object sender, EventArgs args)
   at System.Collections.Specialized.CollectionChangedEventManager.OnCollectionChanged(Object sender, NotifyCollectionChangedEventArgs args)
   at System.Windows.Data.CollectionView.OnCollectionChanged(NotifyCollectionChangedEventArgs args)
   at System.Windows.Data.ListCollectionView.RefreshOverride()
   at System.Windows.Data.CollectionView.RefreshOrDefer()
   at System.Windows.Data.ListCollectionView.ProcessCollectionChanged(NotifyCollectionChangedEventArgs args)
   at System.Windows.Data.CollectionView.OnCollectionChanged(Object sender, NotifyCollectionChangedEventArgs args)
   at System.Collections.ObjectModel.ObservableCollection`1.OnCollectionChanged(NotifyCollectionChangedEventArgs e)
   at System.Collections.ObjectModel.ObservableCollection`1.ClearItems()
   at System.Collections.ObjectModel.Collection`1.Clear()
   at CocoonV4.Modules.CocoonViewsVMs.ManageTemplateDekocastViewModel.SetAllowedDekos(IEnumerable`1 _NewAllowedDekos) in C:\Users\lkottmann\Documents\Visual Studio 2010\Projects\IAV-Cocoon\MAIN\CocoonV4\CocoonV4.Modules.RunningItem\CocoonViewsVMs\ManageTemplateDekocastViewModel.cs:line 83
   at CocoonV4.Modules.CocoonViewsVMs.ManageTemplateDekocastViewModel.LoadTemplates(Nullable`1 param) in C:\Users\lkottmann\Documents\Visual Studio 2010\Projects\IAV-Cocoon\MAIN\CocoonV4\CocoonV4.Modules.RunningItem\CocoonViewsVMs\ManageTemplateDekocastViewModel.cs:line 128
   at Microsoft.Practices.Prism.Commands.DelegateCommand`1.<>c__DisplayClass6.<.ctor>b__2(Object o)
   at Microsoft.Practices.Prism.Commands.DelegateCommandBase.Execute(Object parameter)
   at Microsoft.Practices.Prism.Commands.DelegateCommandBase.System.Windows.Input.ICommand.Execute(Object parameter)
   at System.Windows.Interactivity.InvokeCommandAction.Invoke(Object parameter)
   at System.Windows.Interactivity.TriggerBase.InvokeActions(Object parameter)
   at System.Windows.Interactivity.EventTriggerBase.OnEvent(EventArgs eventArgs)
   at System.Windows.Interactivity.EventTriggerBase.OnEventImpl(Object sender, EventArgs eventArgs)
   at System.Windows.Controls.SelectionChangedEventArgs.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.RaiseEvent(RoutedEventArgs e)
   at System.Windows.Controls.ComboBox.OnSelectionChanged(SelectionChangedEventArgs e)
   at System.Windows.Controls.Primitives.Selector.InvokeSelectionChanged(List`1 unselectedItems, List`1 selectedItems)
   at System.Windows.Controls.Primitives.Selector.SelectionChanger.End()
   at System.Windows.Controls.Primitives.Selector.SelectionChanger.SelectJustThisItem(Object item, Boolean assumeInItemsCollection)
   at System.Windows.Controls.ComboBox.NotifyComboBoxItemMouseUp(ComboBoxItem comboBoxItem)
   at System.Windows.Controls.ComboBoxItem.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.InvokeImpl(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.Application.RunDispatcher(Object ignore)
   at System.Windows.Application.RunInternal(Window window)
   at System.Windows.Application.Run(Window window)
   at System.Windows.Application.Run()
   at CocoonV4.App.Main() in C:\Users\lkottmann\Documents\Visual Studio 2010\Projects\IAV-Cocoon\MAIN\CocoonV4\CocoonV4\obj\x86\Debug\App.g.cs:line 0
   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.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadHelper.ThreadStart()

More EDIT:

I isolated the problem to a single ComboBox declarated as follow:

<custom:CComboBox x:Name="cmbFirstDko"
                  ItemsSource="{Binding Path=DataContext.MyFirstCollection, ElementName=myViewName}"
                  SelectedValue="{Binding anObjectID, Mode=TwoWay}"
                  SelectedValuePath="anObjectID">

Please note that the anObjectID property in SelectedValue comes from the ListView's DataContext (this ComboBox is displaying part of an item of that ListView), whereas the anObjectID in SelectedValuePath refers to a property that each item in DataContext.MyFirstCollection has.

This allows me to select a different ComboBoxItem for each element of the ListView.

I hope my explanation is clear, otherwise tell me in the comments and i'll try to clarify.

Breakthrough: The ComboBoxes have their DataContext set to {DisconnectedItem}, this is the result of the work of so-called SentinelObjects which intervene when there's a binding between 2 collections, as in my example.

It is actually officialy a bug of the framework, and it has been fixed for the next version, see this MS Bug Page

Does anyone know of a workaround?

EDIT: There used to be an answer linking to my blog, but while I move it people downvoted the answer. I got sick of it so now it'll be back when it's ready.

Answer

Kumareshan picture Kumareshan · Oct 15, 2013
  1. No need to call RaisePropertyChanged for MyObsCollection, because ObservableCollection internal implements INotifiyProperty Changed.
  2. I think it is Crashing while assign the value(during set call), this will happen when you try to assign a collection of one type collection of another type. You have to create object of the MyCustomType and should be added to the MyObsCollection instead of directly assigning a collection of different type to MyObsCollection

It would be great if could post the entire code or piece of code where u assign the or add objects to MyObsCollection

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