Question

I have a tool that generates reports in Excel using Interop and using a lot of conditional formatting data bars.

I found that the performance hit was HUGE when adding the conditional formats through Interop.

The question is: Is there a way to enhance the performance of Interop conditional formatting?

Answer 1

And today, after searching a lot and even considering rewriting my code entirely to use different OpenXML libraries, I finally found the solution in MSDN:

Worksheet.EnableFormatConditionsCalculation Property

Just add this line of code before you add conditional formats with Interop, and you’ll notice a HUGE performance boost in your application:

// Disable conditional format calculations to enhance speed
Sheet.EnableFormatConditionsCalculation = false;

Hope this helps others, since I’ve been looking for this for ages and I never found it until today. 🙂

Note: Apparently, you don’t need to set this property back to true before saving the Excel. The Excels I saved so far have the conditional format calculations enabled when I open them, even I didn’t set this back to true when saving them with Interop.