Drag from a read-only items source (without removing items)

[Valeriu]

I'm trying to accomplish a scenario and I'm failing to find a decent info about your drag and drop implementation. Help is seriously lacking info and have mixed RadDragAndDropManager and DragDropManager content which doesn't helps at all.

My scenario:

 - Read only list (displayed in a RadListBox)

 - Another RadListBox that should be populated with items from first one

 - A Converter that converts items from one format to another

So I would like that items from first list aren't removed. In my current implementation I'm receiving an exception when dropping items on second list telling me that ItemsSource from the read-only listbox cannot be modified.

Any hints on how to accomplish this simple requirement?

Thanks

Exception details:

System.InvalidOperationException was unhandled by user code
  HResult=-2146233079
  Message=Operation is not valid while ItemsSource is in use. Access and modify elements with ItemsControl.ItemsSource instead.
  Source=PresentationFramework
  StackTrace:
       at System.Windows.Controls.ItemCollection.CheckIsUsingInnerView()
       at System.Windows.Controls.ItemCollection.Remove(Object removeItem)
       at Telerik.Windows.DragDrop.Behaviors.DragDropBehavior`1.RemoveItems(IList source, IEnumerable items) in c:\TB\117\WPF_Scrum\Release_WPF\Sources\Development\Core\Controls\DragDropManager\Behaviors\Common\DragDropBehavior.cs:line 186
       at Telerik.Windows.DragDrop.Behaviors.DragDropBehavior`1.DragDropCompleted(TState state) in c:\TB\117\WPF_Scrum\Release_WPF\Sources\Development\Core\Controls\DragDropManager\Behaviors\Common\DragDropBehavior.cs:line 161
       at Telerik.Windows.DragDrop.Behaviors.DragDropHelper`2.DragDropCompleted(FrameworkElement dropItemsControl, Object data, Type itemType, Boolean wasCanceled) in c:\TB\117\WPF_Scrum\Release_WPF\Sources\Development\Core\Controls\DragDropManager\Behaviors\Common\DragDropHelper.cs:line 228
       at Telerik.Windows.DragDrop.Behaviors.DragDropHelper`2.CompleteDrag(Object data, DragDropEffects effects) in c:\TB\117\WPF_Scrum\Release_WPF\Sources\Development\Core\Controls\DragDropManager\Behaviors\Common\DragDropHelper.cs:line 398
       at Telerik.Windows.DragDrop.Behaviors.DragDropHelper`2.DragDropCompleted(Object sender, DragDropCompletedEventArgs e) in c:\TB\117\WPF_Scrum\Release_WPF\Sources\Development\Core\Controls\DragDropManager\Behaviors\Common\DragDropHelper.cs:line 392
       at Telerik.Windows.DragDrop.DragDropCompletedEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget) in c:\TB\117\WPF_Scrum\Release_WPF\Sources\Development\Core\Controls\DragDropManager\DragDropCompletedEventArgs.cs:line 61
       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 Telerik.Windows.DragDrop.IInputElementExtensions.RaiseEvent(DependencyObject d, RoutedEventArgs routedEventArgs) in c:\TB\117\WPF_Scrum\Release_WPF\Sources\Development\Core\Controls\DragDropManager\DependencyObjectExtensions.cs:line 82
       at Telerik.Windows.DragDrop.DragDropManager.DoDragDrop(DependencyObject dragSource, Object data, DragDropEffects allowedEffects, DragDropKeyStates initialKeyState, Object dragVisual, Point relativeStartPoint, Point dragVisualOffset) in c:\TB\117\WPF_Scrum\Release_WPF\Sources\Development\Core\Controls\DragDropManager\DragDropManager.cs:line 1026
       at Telerik.Windows.DragDrop.DragInitializer.StartDrag() in c:\TB\117\WPF_Scrum\Release_WPF\Sources\Development\Core\Controls\DragDropManager\DragInitializer.cs:line 236
       at Telerik.Windows.DragDrop.DragInitializer.StartDragPrivate(UIElement sender) in c:\TB\117\WPF_Scrum\Release_WPF\Sources\Development\Core\Controls\DragDropManager\DragInitializer.cs:line 186
       at Telerik.Windows.DragDrop.DragInitializer.DragSourceOnMouseMove(Object sender, MouseEventArgs e) in c:\TB\117\WPF_Scrum\Release_WPF\Sources\Development\Core\Controls\DragDropManager\DragInitializer.cs:line 163
       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()
       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)
  InnerException:

[Valeriu]

Overriding the DragDropManager.DragDropCompleted allowed me to implement my scenario.

[Dimitrina]

Hi,

 Thank you for the update. I will as well suggest you to check our Drag and Drop Demos showing working examples on how to benefit from DragDropManager.

Regards,
Didie
the Telerik team