Insert Group Headers within GridView

The idea is to group the data in the Grid View, then insert a group header for each group of items.
References:
http://blog.zygonia.net/PermaLink,guid,c093836d-8d97-4e5b-8a1c-8218742cb686.aspx
http://www.agrinei.com/gridviewhelper/gridviewhelper_en.htm
http://www.asp.net/learn/data-access/tutorial-27-cs.aspx

In a nutshell, we can do the following:
1) Add a RowDataBound event to add additional table row when we encounter new group.
2) Override the Render method to add additional table row when we encounter new group.

Issue at hand:
1) Add "Expand/Collapse" button in the group header, such that upon click, will set the respective rows to visible = true or false.