override to specify the number of rows to be displayed for an on-demand dataView

When setting up a datasource, assigning a value to Count will normally cause the DataSource to manage the data internally. You can still override operations, such as cellText and SortByColumn An on-demand setup should either not set the count property, and override the count getter, or pass false as the 'managed' parameter. The later method causes the view to update automatically when the list count is changed from elsewhere.