When I sort my grid on certain columns and then change the data bound to the grid from a thread other than the main UI thread, I sometimes get a null reference exception.
My setup is basically this:
_gridView.DataSource = myObject.Children;
// user sorts grid
// user requests update from server
make BackgroundWorker to pull from server and update myObject.Children (fields of existing objects and add/remove from list)
show progress dialog on UI thread while data is being pulled from server and put into Children on BackgroundWorker thread
I get this exception:
Looking at my worker thread state when this exception occurs, I get this more complete looking call stack. It looks like this should perhaps being doing an Invoke to move these changes to the grid back to the UI thread.
My setup is basically this:
_gridView.DataSource = myObject.Children;
// user sorts grid
// user requests update from server
make BackgroundWorker to pull from server and update myObject.Children (fields of existing objects and add/remove from list)
show progress dialog on UI thread while data is being pulled from server and put into Children on BackgroundWorker thread
I get this exception:
System.NullReferenceException {"Object reference not set to an instance of an object."} at Telerik.Collections.Generic.AvlTree`1.FixInsert(AvlTreeNode`1 t, AvlTreeNode`1 u, Int32[] ad, Int32 n) at Telerik.Collections.Generic.AvlTree`1.Insert(Int32 index, ValueT value) at Telerik.Collections.Generic.AvlTree`1.InsertWithDuplicates(ValueT value) at Telerik.Collections.Generic.AvlTree`1.Add(ValueT item) at Telerik.WinControls.Data.AvlIndex`1.Perform() at Telerik.WinControls.Data.AvlIndex`1.get_Items() at Telerik.WinControls.Data.RadDataView`1.get_Items() at Telerik.WinControls.Data.RadCollectionView`1.GetEnumerator() at Telerik.WinControls.UI.GridViewInfo.Refresh() at Telerik.WinControls.UI.GridViewInfo.get_ChildRows() at Telerik.WinControls.UI.GridViewTemplate.get_ChildRows() at Telerik.WinControls.UI.GridViewRowInfo.get_Index() at Telerik.WinControls.UI.GridDataRowElement.UpdateAlternatingRowColor() at Telerik.WinControls.UI.GridDataRowElement.ApplyCustomFormatting() at Telerik.WinControls.UI.GridRowElement.UpdateInfo() at Telerik.WinControls.UI.GridDataRowElement.UpdateInfo() at Telerik.WinControls.UI.GridRowElement.Initialize(GridViewRowInfo rowInfo) at Telerik.WinControls.UI.GridRowElement.Attach(GridViewRowInfo row, Object context) at Telerik.WinControls.UI.BaseVirtualizedContainer`1.InsertElement(Int32 position, IVirtualizedElement`1 element, T data) at Telerik.WinControls.UI.BaseVirtualizedContainer`1.UpdateElement(Int32 position, T data) at Telerik.WinControls.UI.ScrollableRowsContainerElement.UpdateElement(Int32 position, GridViewRowInfo data) at Telerik.WinControls.UI.BaseVirtualizedContainer`1.MeasureElements() at Telerik.WinControls.UI.BaseVirtualizedContainer`1.MeasureOverride(SizeF availableSize) at Telerik.WinControls.UI.ScrollableRowsContainerElement.MeasureOverride(SizeF availableSize) at Telerik.WinControls.RadElement.MeasureCore(SizeF availableSize) at Telerik.WinControls.RadElement.Measure(SizeF availableSize) at Telerik.WinControls.UI.RowsContainerElement.MeasureOverride(SizeF availableSize) at Telerik.WinControls.RadElement.MeasureCore(SizeF availableSize) at Telerik.WinControls.RadElement.Measure(SizeF availableSize) at Telerik.WinControls.Layouts.ContextLayoutManager.UpdateLayout() at Telerik.WinControls.Layouts.ContextLayoutManager.UpdateLayoutCallback(ILayoutManager manager)Looking at my worker thread state when this exception occurs, I get this more complete looking call stack. It looks like this should perhaps being doing an Invoke to move these changes to the grid back to the UI thread.
[Managed to Native Transition] mscorlib.dll!System.Type.IsVisible.get() + 0x23 bytes System.dll!System.SecurityUtils.MethodInfoInvoke(System.Reflection.MethodInfo method, object target, object[] args) + 0x30 bytes System.dll!System.ComponentModel.ReflectPropertyDescriptor.GetValue(object component) + 0x5f bytes Telerik.WinControls.dll!Telerik.WinControls.Data.RadListSource<System.__Canon>.GetBoundValue(object dataBoundItem, string propertyName) + 0x3a bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.BoundAccessor.this[Telerik.WinControls.UI.GridViewRowInfo].get(Telerik.WinControls.UI.GridViewRowInfo row) + 0xb7 bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewDateTimeColumn.GetValue(Telerik.WinControls.UI.GridViewRowInfo row, Telerik.WinControls.UI.GridViewDataOperation operation) + 0x15 bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewRowInfoComparer.CompareRows(Telerik.WinControls.UI.GridViewRowInfo x, Telerik.WinControls.UI.GridViewRowInfo y, Telerik.WinControls.Data.SortDescriptorCollection context) + 0x93 bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewRowInfoComparer.Compare(Telerik.WinControls.UI.GridViewRowInfo x, Telerik.WinControls.UI.GridViewRowInfo y) + 0xe bytes Telerik.WinControls.dll!Telerik.Collections.Generic.AvlTree<Telerik.WinControls.UI.GridViewRowInfo>.Insert(Telerik.WinControls.UI.GridViewRowInfo value, bool duplicateallowed, bool overwrite) + 0x114 bytes Telerik.WinControls.dll!Telerik.Collections.Generic.AvlTree<System.__Canon>.InsertWithDuplicates(System.__Canon value) + 0x32 bytes Telerik.WinControls.dll!Telerik.Collections.Generic.AvlTree<System.__Canon>.Add(System.__Canon item) + 0x5 bytes Telerik.WinControls.dll!Telerik.WinControls.Data.AvlIndex<Telerik.WinControls.UI.GridViewRowInfo>.Perform() + 0x2ff bytes Telerik.WinControls.dll!Telerik.WinControls.Data.AvlIndex<Telerik.WinControls.UI.GridViewRowInfo>.Items.get() + 0x10 bytes Telerik.WinControls.dll!Telerik.WinControls.Data.RadDataView<System.__Canon>.Items.get() + 0xe bytes Telerik.WinControls.dll!Telerik.WinControls.Data.RadCollectionView<Telerik.WinControls.UI.GridViewRowInfo>.GetEnumerator() + 0x11 bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewInfo.Refresh() + 0x213 bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewInfo.ChildRows.get() + 0x1f bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewTemplate.ChildRows.get() + 0xa bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.ViewInfoTraverser.SetCollectionForStage(bool initializeCollection) + 0x138 bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.ViewInfoTraverser.ChangeCollectionForward() + 0x49 bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.ViewInfoTraverser.MoveNextCore() + 0x33 bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.ViewInfoTraverser.MoveNext() + 0x3a bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridTraverser.MoveNextCore() + 0x42 bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridTraverser.MoveNext() + 0xd bytes Telerik.WinControls.UI.dll!Telerik.WinControls.UI.ItemScroller<Telerik.WinControls.UI.GridViewRowInfo>.UpdateScrollRange() + 0x60 bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.RowScroller.UpdateScrollRange() + 0x19 bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridTableElement.UpdateWhenItemChanged(Telerik.WinControls.UI.DataViewChangedEventArgs args) + 0x94 bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridTableElement.UpdateViewCore(object sender, Telerik.WinControls.UI.DataViewChangedEventArgs args) + 0x1ed bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridTableElement.UpdateView(object sender, Telerik.WinControls.UI.DataViewChangedEventArgs args) + 0x4e bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridTableElement.ProcessTemplateEvent(Telerik.WinControls.UI.GridViewEvent eventData) + 0xc7 bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridTableElement.Telerik.WinControls.UI.IGridViewEventListener.ProcessEvent(Telerik.WinControls.UI.GridViewEvent eventData) + 0x196 bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewEventProcessEntity.ProcessCollection(Telerik.WinControls.UI.GridViewEvent gridEvent, Telerik.WinControls.UI.PriorityWeakReferenceList list, Telerik.WinControls.UI.GridEventProcessMode processMode) + 0xa4 bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewEventProcessEntity.ProcessEvent(Telerik.WinControls.UI.GridViewEvent gridEvent) + 0x35 bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewSynchronizationService.NotifyListeners(Telerik.WinControls.UI.GridViewEvent gridEvent) + 0x8a bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewSynchronizationService.FlushEvents() + 0xda bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewSynchronizationService.DispatchEvent(Telerik.WinControls.UI.GridViewEvent gridEvent) + 0x61 bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewSynchronizationService.DispatchEvent(Telerik.WinControls.UI.GridViewTemplate template, Telerik.WinControls.UI.GridViewEvent eventData, bool postUI) + 0x18b bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewTemplate.DispatchEvent(Telerik.WinControls.UI.GridViewEvent gridEvent, bool postUI) + 0xb bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewTemplate.DispatchDataViewChangedEvent(object sender, Telerik.WinControls.UI.DataViewChangedEventArgs args) + 0xa2 bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewTemplate.OnViewChanged(object sender, Telerik.WinControls.UI.DataViewChangedEventArgs e) + 0x49 bytes Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewTemplate.CollectionView_CollectionChanged(object sender, Telerik.WinControls.Data.NotifyCollectionChangedEventArgs e) + 0x2e bytes Telerik.WinControls.dll!Telerik.WinControls.Data.RadCollectionView<System.__Canon>.OnCollectionChanged(Telerik.WinControls.Data.NotifyCollectionChangedEventArgs args) + 0x3f bytes Telerik.WinControls.dll!Telerik.WinControls.Data.RadDataView<Telerik.WinControls.UI.GridViewRowInfo>.ProcessCollectionChanged(Telerik.WinControls.Data.NotifyCollectionChangedEventArgs args) + 0x11b bytes Telerik.WinControls.dll!Telerik.WinControls.Data.RadCollectionView<System.__Canon>.source_CollectionChanged(object sender, Telerik.WinControls.Data.NotifyCollectionChangedEventArgs e) + 0x23 bytes Telerik.WinControls.dll!Telerik.WinControls.Data.RadListSource<System.__Canon>.OnCollectionChanged(Telerik.WinControls.Data.NotifyCollectionChangedEventArgs e) + 0x1e bytes Telerik.WinControls.dll!Telerik.WinControls.Data.RadListSource<System.__Canon>.ChangeItem(int index, System.__Canon item, string propertyName) + 0xc2 bytes Telerik.WinControls.dll!Telerik.WinControls.Data.RadListSource<System.__Canon>.currencyManager_ListChanged(object sender, System.ComponentModel.ListChangedEventArgs e) + 0x125 bytes System.Windows.Forms.dll!System.Windows.Forms.CurrencyManager.OnListChanged(System.ComponentModel.ListChangedEventArgs e) + 0x15 bytes System.Windows.Forms.dll!System.Windows.Forms.CurrencyManager.List_ListChanged(object sender, System.ComponentModel.ListChangedEventArgs e) + 0x53e bytes System.Data.Entity.dll!System.Data.Objects.ObjectView<System.__Canon>.OnListChanged(System.ComponentModel.ListChangedEventArgs changeArgs) + 0x1f bytes System.Data.Entity.dll!System.Data.Objects.ObjectView<DataAccess.Child>.System.Data.Objects.IObjectView.EntityPropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e) + 0x4d bytes System.Data.Entity.dll!System.Data.Objects.ObjectViewListener.EntityPropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e) + 0x31 bytes System.Data.Entity.dll!System.Data.Objects.DataClasses.StructuralObject.OnPropertyChanged(string property) + 0x31 bytes System.Data.Entity.dll!System.Data.Objects.DataClasses.StructuralObject.ReportPropertyChanged(string property) + 0x23 bytes System.Data.Entity.dll!System.Data.Objects.DataClasses.EntityObject.ReportPropertyChanged(string property) + 0x50 bytes 2 Answers, 1 is accepted
0
Brad
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answered on 07 Feb 2013, 05:14 PM
I have just worked on a form with multiple data bound GridViews that update the database on a BackgroundWorker. To prevent errors like this I call the GridView SuspendLayout and BeginUpdate functions before starting the background worker. In the RunWorkerCompleted event I call EndUpdate and ResumeLayout.
I put them in a couple functions like so, and call them before running the background worker and on completion:
I put them in a couple functions like so, and call them before running the background worker and on completion:
private void setGridsToBeginUpdate(){ this.radGridView1.SuspendLayout(); this.radGridView1.BeginUpdate(); //Repeat for other Grids...}private void setGridsToEndUpdate(){ this.radGridView1.EndUpdate(); this.radGridView1.ResumeLayout(); //Repeat for other Grids...}private void button1_Click(object sender, EventArgs e){
radGridView.EndEdit(); setGridsToBeginUpdate(); //backgroundWorker.RunWorkerAsync()}private void bw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e){ setGridsToEndUpdate();}0
Hi John,
Julian Benkov
the Telerik team
RadGridView does not support cross-thread update operations. This behavior concerns all our UI components and the whole Windows Forms GUI. More information about this topic and how to use the UI in a multithreaded application you can find in the MSDN Documentation.
I hope this information is useful. Let me know if you need further assistance.
Julian Benkov
the Telerik team
Q3'12 SP1 of RadControls for WinForms is out now. See what's new.