As far as I know, Doddle Report doesn't have grouping capability built into the system. According to some of the discussion on the codeplex,
it appears that the creator is also looking for someone to include that functionality.
One work-around I used for different groups was to create an excel report and then use AppendReport()
to get multiple pages in the same report. Unfortunately, the iTextSharp report writer doesn't implement AppendReport()
so I had to use the OpenXml writer for this.