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After switching to the most recent telerik dll's, I have started seeing an exception when I attempt to group by a column in the RadGridView.
(EDIT)
Actually this problem isn't with grouping... it's occuring when I am dragging the column header. I am running in legacy drag and drop mode and after my "OnGridViewDropInfo" event completes, I get this error...
System.ArgumentNullException: Value cannot be null.Parameter name: element at Telerik.Windows.Controls.ChildrenOfTypeExtensions.<GetChildrenRecursive>d__3.MoveNext() at System.Linq.Enumerable.<OfTypeIterator>d__aa`1.MoveNext() at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable`1 source) at Telerik.Windows.Controls.GridView.DragDropHelper.GetElement(Grid cue) at Telerik.Windows.Controls.GridView.DragDropController.OnHeaderCellDragInfo(Object sender, DragDropEventArgs e) at Telerik.Windows.Controls.DragDrop.DragDropEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget) at Telerik.Windows.RadRoutedEventArgs.InvokeHandler(Delegate handler, Object target) at Telerik.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RadRoutedEventArgs routedEventArgs) at Telerik.Windows.RouteItem.InvokeHandler(RadRoutedEventArgs routedEventArgs) at Telerik.Windows.EventRoute.InvokeHandlersImpl(Object source, RadRoutedEventArgs args, Boolean raisedAgain) at Telerik.Windows.EventRoute.InvokeHandlers(Object source, RadRoutedEventArgs args) at Telerik.Windows.RadRoutedEventHelper.RaiseEvent(DependencyObject element, RadRoutedEventArgs args) at Telerik.Windows.DependencyObjectExtensions.RaiseEvent(DependencyObject element, RadRoutedEventArgs e) at Telerik.Windows.Controls.DragDrop.RadDragAndDropManager.DragDropProvider_DragInfo(Object sender, DragDropEventArgs e) at Telerik.Windows.Controls.DragDrop.DragDropProviderBase.RaiseDragInfo() at Telerik.Windows.Controls.DragDrop.DragDropProviderBase.NotifySource() at Telerik.Windows.Controls.DragDrop.DragDropProviderBase.OnDropImpossible() at Telerik.Windows.Controls.DragDrop.SimulatedDragDropProvider.OnRealDrag(IMouseEventArgs e) at Telerik.Windows.Controls.DragDrop.SimulatedDragDropProvider.OnCoverRectangleMouseMoveInternal(IMouseEventArgs e) at Telerik.Windows.Controls.DragDrop.SilverlightDragDropProvider.OnCoverRectangleMouseMove(Object sender, MouseEventArgs e) at MS.Internal.CoreInvokeHandler.InvokeEventHandler(Int32 typeIndex, Delegate handlerDelegate, Object sender, Object args) at MS.Internal.JoltHelper.FireEvent(IntPtr unmanagedObj, IntPtr unmanagedObjArgs, Int32 argsTypeIndex, Int32 actualArgsTypeIndex, String eventName)