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Drag/Drop exception

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TreeView

This is a migrated thread and some comments may be shown as answers.

Tal asked on 25 Jan 2009, 04:12 PM

Hi,
I've created a simple solution to test the RadTreeview.It just initializes a new ObservableCollection of Items like this:

    
             /// <summary> 
        
                /// Interaction logic for Window1.xaml 
        
                /// </summary> 
        
                public partial class Window1 : Window 
        
                { 
        
                    public ObservableCollection<Item> Items 
        
                    { 
        
                        get { return (ObservableCollection<Item>)GetValue(ItemsProperty); } 
        
                        set { SetValue(ItemsProperty, value); } 
        
                    } 
        
                    // Using a DependencyProperty as the backing store for Items.  This enables animation, styling, binding, etc... 
        
                    public static readonly DependencyProperty ItemsProperty = 
        
                        DependencyProperty.Register("Items", typeof(ObservableCollection<Item>), typeof(Window1)); 
        
                    public Window1() 
        
                    { 
        
                        InitializeComponent(); 
        
                        Items = new ObservableCollection<Item>(); 
        
                        Items.Add(new Item("Item 1")); 
        
                        Items.Add(new Item("Item 2")); 
        
                        Items.Add(new Item("Item 3")); 
        
                    } 
        
                } 
        
                public class Item 
        
                { 
        
                    public string Header { get; set; } 
        
                    public ObservableCollection<Item> Items { get; set; } 
        
                    public Item(string header) 
        
                    { 
        
                        Header = header; 
        
                        Items = new ObservableCollection<Item>(); 
        
                    } 
        
                }

and in xaml created a simple HierarchicalDataTemplate:

    
            <Window.Resources> 
        
                    <HierarchicalDataTemplate x:Key="NodeTemplate" ItemsSource="{Binding Path=Items}"> 
        
                        <StackPanel Orientation="Horizontal"> 
        
                            <TextBlock Text="{Binding Path=Header}"/> 
        
                        </StackPanel> 
        
                    </HierarchicalDataTemplate> 
        
                </Window.Resources> 
        
                <Grid> 
        
                    <Telerik:RadTreeView IsDragDropEnabled="True" Name="t"  
        
                                         ItemsSource="{Binding Path=Items, ElementName=window}"  
        
                                         ItemTemplate="{StaticResource NodeTemplate}"> 
        
                    </Telerik:RadTreeView> 
        
                </Grid>

Now, when I am trying to drag "Item 1" to, lets say, "Item 2" it works ok. But if afterwards I am trying to drag "Item 3" to "Item 1" (that is now under "Item 2") I am getting a NullReferenceException with the following stack trace:

    
               at Telerik.Windows.Controls.RadTreeViewItem.CheckStatePropertyChangedConstrainValue(DependencyObject d, Object newValue) 
        
               at System.Windows.DependencyObject.ProcessCoerceValue(DependencyProperty dp, PropertyMetadata metadata, EntryIndex& entryIndex, Int32& targetIndex, EffectiveValueEntry& newEntry, EffectiveValueEntry& oldEntry, Object& oldValue, Object baseValue, CoerceValueCallback coerceValueCallback, Boolean coerceWithDeferredReference, Boolean skipBaseValueChecks) 
        
               at System.Windows.DependencyObject.UpdateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, Boolean coerceWithDeferredReference, OperationType operationType) 
        
               at System.Windows.DependencyObject.SetValueCommon(DependencyProperty dp, Object value, PropertyMetadata metadata, Boolean coerceWithDeferredReference, OperationType operationType, Boolean isInternal) 
        
               at System.Windows.DependencyObject.SetValue(DependencyProperty dp, Object value) 
        
               at Telerik.Windows.Controls.RadTreeViewItem.set_CheckState(ToggleState value) 
        
               at Telerik.Windows.Controls.RadTreeViewItem.SetCheckStateWithNoPropagation(ToggleState state) 
        
               at Telerik.Windows.Controls.RadTreeViewItem.Render(Boolean recursive) 
        
               at Telerik.Windows.Controls.RadTreeViewItem.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.ProcessCollectionChangedWithAdjustedIndex(NotifyCollectionChangedEventArgs args, Int32 adjustedOldIndex, Int32 adjustedNewIndex) 
        
               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.InsertItem(Int32 index, T item) 
        
               at System.Collections.ObjectModel.Collection`1.Add(T item) 
        
               at System.Collections.ObjectModel.Collection`1.System.Collections.IList.Add(Object value) 
        
               at Telerik.Windows.Controls.RadTreeView.EndDrag() 
        
               at Telerik.Windows.Controls.RadTreeView.HandleMouseUp(MouseEventArgs e) 
        
               at Telerik.Windows.Controls.RadTreeView.RadTreeView_MouseLeftButtonUp(Object sender, MouseEventArgs 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.CrackMouseButtonEventAndReRaiseEvent(DependencyObject sender, MouseButtonEventArgs e) 
        
               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.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, Int32 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, Boolean isSingleParameter) 
        
               at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Boolean isSingleParameter, Delegate catchHandler) 
        
               at System.Windows.Threading.Dispatcher.WrappedInvoke(Delegate callback, Object args, Boolean isSingleParameter, Delegate catchHandler) 
        
               at System.Windows.Threading.Dispatcher.InvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Boolean isSingleParameter) 
        
               at System.Windows.Threading.Dispatcher.Invoke(DispatcherPriority priority, Delegate method, Object arg) 
        
               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 Telerik.App.Main() in C:\Documents and Settings\talg\Desktop\TreeViewDrag\Telerik\Telerik\obj\Debug\App.g.cs:line 0 
        
               at System.AppDomain._nExecuteAssembly(Assembly 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) 
        
               at System.Threading.ThreadHelper.ThreadStart()

To make things even worse, it's not constant. It happens in about 50% of the tries.
Thank you in advance,
Tal

Drag/Drop exception

1 Answer, 1 is accepted