Tracking state using ASP.NET AJAX / ICallbackEventHandler | I have a problem with maintaining state in an ASP.NET AJAX page. Short version: I need some way to update the page ViewState after an async callback has been made, to reflect any state changes the server made during the async call. 


This seems to be a common problem, but I will describe my scenario to help explain:


I have a grid-like control which has some JavaScript enhancements - namely, the ability to drag and drop columns and rows. When a column or row is dropped into a new position, an AJAX method is invoked to notify the control server-side and fire a corresponding server-side event ("OnColumnMoved" or "OnRowMoved").


ASP.NET AJAX calls, by default, send the entire page as the request. That way the page goes through a complete lifecycle, viewstate is persisted and the state of the control is restored before the RaiseCallbackEvent method is invoked.


However, since the AJAX call does not update the page, the ViewState reflects the *original* state of the control, even after the column or row has been moved. So the second time a client-side action occurs, the AJAX request goes to the server and the page & control are built back up again to reflect the *first* state of the control, not the state after the first column or row was moved.


This problem extends to many implications. For example if we have a client-side/AJAX action to add a new item to the grid, and then a row is dragged, the grid is built server-side with one less item than on the client-side.


And finally & most seriously for my specific example, the actual data source object we are acting upon is stored in the page ViewState. That was a design decision to allow keeping a stateful copy of the manipulated data which can either be committed to DB after many manipulations or discarded if the user backs out. That is very difficult to change.


So, again, I need a way for the page ViewState to be updated on callback after the AJAX method is fired.