title: Can't add a child group in ReportViewer - Visual Studio 2010
body: <p>I am trying to add a child group on a report (RDLC file) and I can't get it to work.  If I right click on the details line of the Tablix it lets me select "Add Group" but then the "Child Group..." option is grayed out.</p>
  
  <p>Please help.  Thanks.</p>