Dear,
You have to use and configure updatepanel triggers and give any control BUTTON,DROPDONWLIST as triggers.
<Triggers>
</Triggers>
ASP.NET Ajax Extension - Update Panel Example with Trigger[
^]
above link will help you to find solutions.
Let me know if you have any further query.
Please, go through above suggestion.
If its your answer, please mark as solution.
Best of luck for hunting solutions.
Thank you.
Regards,
Manoj Kalla