I have a SelectionDrag event where I want to examine the SelectedRowsCollection, verify a constraint of the ListObject of each row.  If the ListObject fails the constraint I want to purge it from the SelectedRowsCollection.

 There is no public method on SelectedRowsCollection to remove a row, so I declare another SelectedRowsCollection and attempt to add the valid rows to the alternate collection, and continue the DragDrop with the valid rows.

 However when I add to the SelectedRowsCollection, I get a null reference exception.  Neither the SelectedRowsCollection nor the row is null.  This has to be something from the internal workings of SelectedRowsCollection.Add().  Is this a bug?  It seems like one.  Any Suggestions?

 Here is the code:

             SelectedRowsCollection selectedRows = ((UltraGrid)sender).Selected.Rows;
            SelectedRowsCollection finalRows = new SelectedRowsCollection();

            foreach (UltraGridRow row in selectedRows)
            {
                DomainObject domainObj = (DomainObject) row.ListObject;

                if (NotValid)
                {
                   continue;
                }

                finalRows.Add(row); // Exception is thrown here
            }

            if (finalRows.Count > 0)
            {
                ((UltraGrid)sender).DoDragDrop(finalRows, DragDropEffects.Move);
            }

Here is the stack trace

   at Infragistics.Win.UltraWinGrid.SelectedRowsCollection.AddRange(UltraGridRow[ rows, Boolean ensureRowsOrdered, Boolean fireSlectionChangeEvent)
   at Infragistics.Win.UltraWinGrid.SelectedRowsCollection.AddRange(UltraGridRow[ rows)
   at Infragistics.Win.UltraWinGrid.SelectedRowsCollection.Add(UltraGridRow row)
   at MyForm.Grid_SelectionDrag(Object sender, CancelEventArgs e) :line 330
   at Infragistics.Win.UltraWinGrid.UltraGrid.OnSelectionDrag(CancelEventArgs e)
   at Infragistics.Win.UltraWinGrid.UltraGrid.FireEvent(GridEventIds id, EventArgs e)
   at Infragistics.Win.UltraWinGrid.UltraGrid.Infragistics.Win.ISelectionManager.OnDragStart(ISelectableItem item, Point mousePosition)
   at Infragistics.Win.SelectionStrategyBase.DragStart()
   at Infragistics.Win.SelectionStrategyExtended.OnMouseMove(ISelectableItem item, MouseMessageInfo& msginfo)
   at Infragistics.Win.SelectionStrategyExtended.OnMouseMessage(ISelectableItem item, MouseMessageInfo& msginfo)
   at Infragistics.Win.ControlUIElementBase.ProcessMouseMoveHelper(Object sender, MouseEventArgs e)
   at Infragistics.Win.ControlUIElementBase.ProcessMouseMove(Object sender, MouseEventArgs e)
   at System.Windows.Forms.MouseEventHandler.Invoke(Object sender, MouseEventArgs e)
   at System.Windows.Forms.Control.OnMouseMove(MouseEventArgs e)
   at System.Windows.Forms.Control.WmMouseMove(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)