asp:chart behaves badly in update control

I put a chart control in an update panel.  When the user clicks on the chart, it should change some other things in the  update panel.  But the entire page is refreshing, which is bad.  Other controls in the update panel behave correctly, but not the chart.  I do add most of the chart attributes to the chart from code in the code-behind, even the "postback" attribute.  Still, it should work.  Has anyone else run into this?
Thanks
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