“Index was outside the bounds of the array” on Infragistics UltraGrid when OnPaint is called

Question

I've binded my grid's DataSource to a BindingSource object which i update from another thread. I've wrote the following code:

    protected override void OnPaint(PaintEventArgs pe)
    {
        if (this.InvokeRequired)
        {
            this.Invoke(new OnPaintMethodInvoker(this.OnPaint), pe);
        }
        else
        {
            try
            {
                    base.OnPaint(pe);
            }
            catch 
            {
            }
        }
    }

And two things happens to me: 1. the Invoke is never being called (i guess the ultragrid know how to handle it) 2. when i play with the screen (mouseover/resize) while the data is being updated - i recieve the following exception:

Index was outside the bounds of the array.

    at Infragistics.Shared.SparseArray.GetItemAtScrollIndex(Int32 scrollIndex, ICreateItemCallback createItemCallback)
   at Infragistics.Win.UltraWinGrid.ScrollCountManagerSparseArray.GetItemAtScrollIndex(Int32 scrollIndex, Boolean allocate)
   at Infragistics.Win.UltraWinGrid.RowsCollection.GetRowAtScrollIndex(Int32 scrollIndex, Boolean allocate)
   at Infragistics.Win.UltraWinGrid.RowsCollection.get_IsLastScrollableRowNotAllocatedYet()
   at Infragistics.Win.UltraWinGrid.RowScrollRegion.IsLastScrollableRowVisible(ScrollbarVisibility colScrollbarVisibility)
   at Infragistics.Win.UltraWinGrid.RowScrollRegion.GetMaxScrollPosition(Boolean scrollToFill)
   at Infragistics.Win.UltraWinGrid.RowScrollRegion.EnsureScrollRegionFilled(Boolean calledFromRegenerateVisibleRows)
   at Infragistics.Win.UltraWinGrid.RowScrollRegion.RegenerateVisibleRows(Boolean resetScrollInfo)
   at Infragistics.Win.UltraWinGrid.RowScrollRegion.RegenerateVisibleRows()
   at Infragistics.Win.UltraWinGrid.RowScrollRegion.WillScrollbarBeShown(ScrollbarVisibility assumeColScrollbarsVisible)
   at Infragistics.Win.UltraWinGrid.ScrollRegionBase.WillScrollbarBeShown()
   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.UIElement.Draw(Graphics graphics, Rectangle invalidRectangle, Boolean doubleBuffer, AlphaBlendMode alphaBlendMode, 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, Size elementSize)
   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 MyProject.Common.UI.Controls.GridControl.OnPaint(PaintEventArgs pe) 

Anyone knows what could be the problem? I've tried to put lock(this) around the base.OnPaint(pe) but it didn't help.

Answer 1

You should not update the data source of a bound control on a background thread. Any updates that are being done to the list that you are bound to should be first marshaled back to the UI thread and the updates should happen there.

When you update the list that the WinGrid is bound to on a background thread this triggers event handlers that respond to changes in your data to be executed on the background thread rather than on the UI thread which causes problems because there are only a few members of Control that are actually thread safe.

You may also want to refer to the Infragistics forums where Mike Saltzman has answered similar questions.