Extender control 'CalendarExtender2' is not a registered extender control. Extender controls must be registered using RegisterExtenderControl()

Hello sir i have used your code to export <div> to pdf & it works fine but when i am using a ajax controls in a <div> tag then it gives me error message i.e :-

"

Extender control 'CalendarExtender2' is not a registered extender control. Extender controls must be registered using RegisterExtenderControl() before calling RegisterScriptDescriptors(). Parameter name: extenderControl

"

please give a solution to resolve it...

Thanks in advance