Will this help if you change this line
<add key="ChartImageHandler" value="storage=file;timeout=20;dir=c:\TempImageFiles\;" />
TO
<add key="ChartImageHandler" value="storage=memory;deleteAfterServicing=true;" />
The reason I recommend that changes because, I'm using that chart control also in one of my article.
ASP.NET AJAX MultiHandleSliderExtender - Slide by Year and Month[
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Here is the working example using the recommend setting:
ASP.NET MultiHandleSliderExtender - Slide by Year and Month[
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