This example demonstrates how you can implement a Drill-Down feature for a report displayed in the ASP.NET MVC DocumentViewer extension.
The main idea of this approach is to store the expanded state of report categories. As this is a web application, a Session is used to store it. Then depending on the category's expanded state its product list is shown or hidden. The DetailReportBand.BeforePrint event handler is used for this purpose.
To make the expand/collapse button working in a web report its HtmlItemCreated event handler is used to add required HTML attributes to it. When the expand button is clicked a client-side function is executed and a callback is sent to the CallbackPanel. In the controller, the expanded state of report categories is updated, and the report is updated.