Sure, I will post a sample project. But this error doesnt happen in dev machine, it happens only in  few customer machines...

Mike,

I've similar issue with UltraWinGrid that I am binding to BindingList<MyClass>. It was working all fine until recently I added a couple of fields (Enum and string fields) to my class that I am updating in separate thread spawned by Task(TPL). I am not adding new items in DataSource itself but i am just changing data in BindingList and Ultragrid throws following error once out of 4-5 times I update the object. The dll version for UltraWinGrid is 13.1.20131.2124.

Also, I've changed my code as following recently to update the row display in case the object is modified in seperate thread.

 private void ultraGrid1_InitializeRow(object sender, InitializeRowEventArgs e)
        {
            try
            {
                this.Grid.SuspendRowSynchronization();
                FileWatchConfiguration fwc = e.Row.ListObject as FileWatchConfiguration;

                if (!bInitializing)
                {
                    if (fwc != null)
                    {
                        SetStatusCellBackColor(fwc.Status, e.Row.Cells["Status"]);
                        this.Grid.DisplayLayout.PerformAutoResizeColumns(false, PerformAutoSizeType.AllRowsInBand);
                    }
                }               
            }
            finally
            {
                this.Grid.ResumeRowSynchronization();
            }
        }

Here is the exception I am seeing. Is there anything I can do to prevent the error? I am thinking about adding an unbound column and changing its content as part of ultraGrid1_InitializeRow. But, i don't want to add something silly like that if there is a better way to address it.

************** Exception Text **************

System.IndexOutOfRangeException: Index was outside the bounds of the array.

   at System.Array.Clear(Array array, Int32 index, Int32 length)

   at System.Collections.Generic.Dictionary`2.Clear()

   at Infragistics.Win.UltraWinGrid.UltraGridLayout.EndCaching()

   at Infragistics.Win.UltraWinGrid.RowScrollRegion.RegenerateVisibleRows(Boolean resetScrollInfo)

   at Infragistics.Win.UltraWinGrid.RowScrollRegion.WillScrollbarBeShown(ScrollbarVisibility assumeColScrollbarsVisible)

   at Infragistics.Win.UltraWinGrid.ViewStyleBase.FitColumnsToWidth()

   at Infragistics.Win.UltraWinGrid.BandsCollection.CalculateBandMetrics(Int32 pass)

   at Infragistics.Win.UltraWinGrid.BandsCollection.CalculateBandMetrics()

   at Infragistics.Win.UltraWinGrid.ColScrollRegionsCollection.InitializeMetricsHelper()

   at Infragistics.Win.UltraWinGrid.ColScrollRegionsCollection.InitializeMetrics()

   at Infragistics.Win.UltraWinGrid.RowScrollRegion.RegenerateVisibleRows(Boolean resetScrollInfo)

   at Infragistics.Win.UltraWinGrid.RowScrollRegion.WillScrollbarBeShown(ScrollbarVisibility assumeColScrollbarsVisible)

   at Infragistics.Win.UltraWinGrid.RowScrollRegion.PositionScrollbar(Boolean resetScrollInfo)

   at Infragistics.Win.UltraWinGrid.ScrollRegionBase.SetOriginAndExtent(Int32 origin, Int32 extent)

   at Infragistics.Win.UltraWinGrid.RowScrollRegion.SetOriginAndExtent(Int32 origin, Int32 extent)

   at Infragistics.Win.UltraWinGrid.DataAreaUIElement.ResizeRowScrollRegions()

   at Infragistics.Win.UltraWinGrid.DataAreaUIElement.PositionChildElements()

   at Infragistics.Win.UIElement.VerifyChildElements(ControlUIElementBase controlElement, Boolean recursive)

   at Infragistics.Win.UltraWinGrid.DataAreaUIElement.VerifyChildElements(ControlUIElementBase controlElement, Boolean recursive)

   at Infragistics.Win.UltraWinGrid.DataAreaUIElement.set_Rect(Rectangle value)

   at Infragistics.Win.UltraWinGrid.UltraGridUIElement.PositionChildElements()

   at Infragistics.Win.UIElement.VerifyChildElements(ControlUIElementBase controlElement, Boolean recursive)

   at Infragistics.Win.UltraWinGrid.UltraGridUIElement.VerifyChildElements(ControlUIElementBase controlElement, Boolean recursive)

   at Infragistics.Win.UIElement.DrawHelper(Graphics graphics, Rectangle invalidRectangle, Boolean doubleBuffer, AlphaBlendMode alphaBlendMode, Boolean clipText, Boolean forceDrawAsFocused, Boolean preventAlphaBlendGraphics)

   at Infragistics.Win.ControlUIElementBase.Draw(Graphics graphics, Rectangle invalidRectangle, Boolean doubleBuffer, AlphaBlendMode alphaBlendMode, Size elementSize, Boolean preventAlphaBlendGraphics)

   at Infragistics.Win.ControlUIElementBase.Draw(Graphics graphics, Rectangle invalidRectangle, Boolean doubleBuffer, AlphaBlendMode alphaBlendMode)

   at Infragistics.Win.UltraWinGrid.UltraGridUIElement.Draw(Graphics graphics, Rectangle invalidRectangle, Boolean doubleBuffer, AlphaBlendMode alphaBlendMode)

   at Infragistics.Win.UltraControlBase.OnPaint(PaintEventArgs pe)

   at Infragistics.Win.UltraWinGrid.UltraGrid.OnPaint(PaintEventArgs pe)

   at System.Windows.Forms.Control.PaintWithErrorHandling(PaintEventArgs e, Int16 layer)

   at System.Windows.Forms.Control.WmPaint(Message& m)

   at System.Windows.Forms.Control.WndProc(Message& m)

   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(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)

************** Loaded Assemblies **************

Multithreading and databinding do not mix well. You cannot modify or even examine the data in the grid's DataSource (or even a BindingSource) on anything other than the UI thread safely. There's no way to do that, because you cannot properly marshal that communication across the threads since you are not in control of that communication. 

Thanks for the info Mike. I'll try to invoke the property change on main thread. I am not getting this exception frequently so i won't know if it fixed my issue for sure. :-)

That's one of the hallmarks of a threading issue - it happens intermittently.