What I need to do to set TreeGrid to be accessible by TAB key in standard tab order at page?
TreeGrid is not by default accessible by tab key. To permit this, you need to write some JavaScript code: 1) Write TreeGrid event handler OnTabOutside. In this event focus previous or next control in tab order. 2) Write HTML event handler onkeydown for previous and next control in tab order and in the code call TreeGrid function TabInside.