1. Feedback
  2. WPF
  3. 11820

Welcome to the WPF feedback portal. We’re happy you’re here! If you have feedback on how to improve the WPF, we’d love to hear it!

  • Check out the features or bugs others have reported and vote on your favorites. Feedback will be prioritized based on popularity.
  • If you have feedback that’s not listed yet, submit your own.

Thanks for joining our community and helping improve Syncfusion products!

1
Vote

Null reference Exception when drag and drop item from ListBox to TreeViewAdv

Null reference Exception occurs when drag and drop the item from ListBox to TreeViewAdv. On analyzing, the data variable which is set as ObservableCollection of the e.OriginalSource is of different type. So the data value is null whose value we haven't checked before accessing the data's count property.

Replication Steps

1. Run the sample.

2. Drag and drop from listbox to TreeViewAdv.

3. Note that the exception occurs.


Stack trace

at Syncfusion.Windows.Tools.Controls.TreeViewAdvDragDropController.ProcessOnDrop(TreeViewAdv control, DragEventArgs args)

at Syncfusion.Windows.Tools.Controls.TreeViewAdv.OnDrop(DragEventArgs e)

at System.Windows.UIElement.OnDropThunk(Object sender, DragEventArgs e)

at System.Windows.DragEventArgs.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.OleDropTarget.RaiseDragEvent(RoutedEvent dragEvent, Int32 dragDropKeyStates, Int32& effects, DependencyObject target, Point targetPoint)

at System.Windows.OleDropTarget.MS.Win32.UnsafeNativeMethods.IOleDropTarget.OleDrop(Object data, Int32 dragDropKeyStates, Int64 point, Int32& effects)

at MS.Win32.UnsafeNativeMethods.DoDragDrop(IDataObject dataObject, IOleDropSource dropSource, Int32 allowedEffects, Int32[] finalEffect)

at System.Windows.OleServicesContext.OleDoDragDrop(IDataObject dataObject, IOleDropSource dropSource, Int32 allowedEffects, Int32[] finalEffect)

at System.Windows.DragDrop.OleDoDragDrop(DependencyObject dragSource, DataObject dataObject, DragDropEffects allowedEffects)

at System.Windows.DragDrop.DoDragDrop(DependencyObject dragSource, Object data, DragDropEffects allowedEffects)

at SampleListTree.MainWindow.ListSource_MouseMove(Object sender, MouseEventArgs e) in D:\Volume 1, 2020\Support\Feb 5\SampleListTree_1a34df68\SampleListTree\MainWindow.xaml.cs:line 152

at System.Windows.Input.MouseEventArgs.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()