A PostBack trigger will always refresh entire page as it calls all the PageLifeCycle events.
To add a trigger to a UpdatePanel, at the end of </ContentTemplate>
write the Triggers
<Triggers>
<asp:AsyncPostBackTrigger ControlID="Button1" />
</Triggers>
If you want a PostBackTrigger then Replace the AsyncPostBackTrigger with PostBackTrigger in the above snippet.
Make sure that ChildAsTrigger property of UpdatePanel is set to True
Refer :
https://msdn.microsoft.com/en-us/library/bb399001.aspx[
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