Object reference not set to an instance of an object. at Telerik.WinControls.UI.GridViewEditManager.OnPositionChanging

[CHRIS]

Telerik.WinControls.GridView version 2012.3.1211.20

Hi Everyone,

I am using GridView's RowSourceNeeded to populate child table when [+] is clicked... it works fine when initial load, however when master table gets refreshed by assigning the DataSource to different collection, it throws following error when [+] is clicked to populate child table.
It seems the child table was populated OK, but it still throws the exception anyway.

Any help/suggestions/ideas are appreciated greatly.  Thank you.

System.NullReferenceException: Object reference not set to an instance of an object.
   at Telerik.WinControls.UI.GridViewEditManager.OnPositionChanging(PositionChangingEventArgs args)
   at Telerik.WinControls.UI.GridViewEditManager.Telerik.WinControls.UI.IGridViewEventListener.PreProcessEvent(GridViewEvent eventData)
   at Telerik.WinControls.UI.GridViewEventProcessEntity.ProcessCollection(GridViewEvent gridEvent, PriorityWeakReferenceList list, GridEventProcessMode processMode)
   at Telerik.WinControls.UI.GridViewSynchronizationService.NotifyListeners(GridViewEvent gridEvent)
   at Telerik.WinControls.UI.GridViewSynchronizationService.FlushEvents()
   at Telerik.WinControls.UI.GridViewSynchronizationService.DispatchEvent(GridViewEvent gridEvent)
   at Telerik.WinControls.UI.GridViewSynchronizationService.RaiseCurrentChanged(GridViewTemplate template, GridViewRowInfo row, GridViewColumn column, Boolean user)
   at Telerik.WinControls.UI.GridViewRowInfo.OnIsCurrentPropertyChanging(PropertyChangingEventArgsEx args)
   at Telerik.WinControls.UI.GridViewRowInfo.OnPropertyChanging(PropertyChangingEventArgsEx args)
   at Telerik.WinControls.UI.GridViewHierarchyRowInfo.OnPropertyChanging(PropertyChangingEventArgsEx args)
   at Telerik.WinControls.UI.GridViewRowInfo.SetBooleanProperty(String propertyName, Int32 propertyKey, Boolean value)
   at Telerik.WinControls.UI.MasterGridViewTemplate.ChangeCurrentRow(GridViewRowInfo oldRow, GridViewRowInfo row, GridViewTemplate viewTemplate)
   at Telerik.WinControls.UI.MasterGridViewTemplate.SetPositionCore(GridViewRowInfo newRow, GridViewColumn newColumn, GridViewRowInfo oldRow, GridViewColumn oldColumn, Boolean validateRowChange)
   at Telerik.WinControls.UI.MasterGridViewTemplate.SetPosition(GridViewRowInfo row, GridViewColumn column, Boolean validateRowChange)
   at Telerik.WinControls.UI.MasterGridViewTemplate.ProcessCurrentChanged(GridViewEvent eventData)
   at Telerik.WinControls.UI.MasterGridViewTemplate.ProcessEventCore(GridViewEvent eventData)
   at Telerik.WinControls.UI.GridViewEventProcessEntity.ProcessCollection(GridViewEvent gridEvent, PriorityWeakReferenceList list, GridEventProcessMode processMode)
   at Telerik.WinControls.UI.GridViewSynchronizationService.NotifyListeners(GridViewEvent gridEvent)
   at Telerik.WinControls.UI.GridViewSynchronizationService.FlushEvents()
   at Telerik.WinControls.UI.GridViewSynchronizationService.DispatchEvent(GridViewEvent gridEvent)
   at Telerik.WinControls.UI.GridViewSynchronizationService.RaiseCurrentChanged(GridViewTemplate template, GridViewRowInfo row, GridViewColumn column, Boolean user)
   at Telerik.WinControls.UI.BaseGridNavigator.SelectCore(GridViewRowInfo row, GridViewColumn column)
   at Telerik.WinControls.UI.GridRowBehavior.SelectPositionOnMouseDownLeft(MouseEventArgs e, GridRowElement rowElement, GridCellElement cellElement)
   at Telerik.WinControls.UI.GridRowBehavior.OnMouseDownLeft(MouseEventArgs e)
   at Telerik.WinControls.UI.GridRowBehavior.OnMouseDown(MouseEventArgs e)
   at Telerik.WinControls.UI.BaseGridBehavior.OnMouseDown(MouseEventArgs e)
   at Telerik.WinControls.UI.RadGridView.OnMouseDown(MouseEventArgs e)
   at System.Windows.Forms.Control.WmMouseDown(Message& m, MouseButtons button, Int32 clicks)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at Telerik.WinControls.RadControl.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

[George]

Hello Chris,

Thank you for contacting Telerik Support.

You should not change the DataSource in the RowSourceNeeded event. You can either only add/remove rows or try to replace the collection on the ChildViewExpanded event. Additionally you can read more about Load-On-Demand in this help article - http://www.telerik.com/help/winforms/gridview-hierarchical-grid-load-on-demand-hierarchy.html.

If you still experience issues, feel free to contact me back with a sample project which can help me get your idea and properly investigate your case.

I hope this helps.

Regards,
George
Telerik

[CHRIS]

Hi George,

Thanks for the reply.

The problem was not really caused by RowSourceNeeded event.

I have two gridviews and they shared same Child templates and HierachyDataProvider...

I created dedicated Child templates and HierachyDataProvider for each GridView and the exception seems gone.

Regards,


Chris

[George]

Hi Chris,

I am glad that you resolved your issue.

Should you have any other questions, do not hesitate to ask.
 
Regards,
George
Telerik