reportviewer.LocalReport.GetTotalPages（）有时返回1或2

In my c# winforms application I'm using a user control, and added my report viewer and a custom toolbar. I want to create a custom navigation for it as well. But, for some reason when I want to check the total number of pages to decide whether or not to show the navigation buttons, it sometimes returns 1 or 2... I've ran out of ideas and not quite sure where to go from here.. application I'm using a user