How to script manager Async Post Back Timeout on runtime

If you have script manager on Master page and need to exceed AsyncPostBackTimeout only on specific page than.
add this code line  in page_load event of your page.

ScriptManager _scriptMan = ScriptManager.GetCurrent(this);
_scriptMan.AsyncPostBackTimeout = 3600 * 15;

This will set AsyncPostBackTimeout upto 15 minutes.

Thakns
Mahesh