DrillDown behavior can be implemented with help of Hyperlinks.
The idea is the following:
- There are TextBoxes with plus/minus Button. They have Hyperlink property which identifies which group to hide/show.
- There is a static dictionary on the form which stores which group is shown or collapsed.
- There is a hyperlink handler which expands/collapses group in the dictionary (sets true or false) and calls rendering
- Visibility of the groups is handled in the scripts and retrieves values from the dictionary mentioned above.
You can find sample here: