WebDataGrid - AJAX Postback vs Full Page Postback

For the older UltraWebGrid, we were able to use grid.IsXmlHttpRequest to differentiate between the grid's AJAX postback vs a full page postback, where the AJAX postback was initiated by grid.invokeXmlHttpRequest(...).

In the new WebDataGrid, is there a way to differentiate between a full page postback vs the AJAX postback of the grid, say in the grid Load event handler? I want to perform different actions depending upon how the grid is posted back.

I'm using the following Javascript perform an AJAX postback on a WebDataGrid to retrieve data from a database.

    var grid = $find("WebDataGrid1");
    var callbackObject = grid._callbackManager.createCallbackObject();