I have a column in my XamDataGrid, "Amount" that shows as Currency.  The "Average" summary works, but does not display it as currency. I have a "Total" summary definition that includes StringFormat="{}Total: {0:C}" so that it does show as currency (the $).  However, I do NOT want the average to initially be shown when the grid is displayed, only if the user selects to show "Average".  It seems that if I define a SummaryDefinition for the Caluclator type, it automatically displays by default.  How can i change to not showing it initially?  Thanks