Thank you for the information, I'm moving this forum thread to the SpreadProcessing forum category.
The process of exporting a workbook to XLSX format basically converts that object to a binary array. For convenience, the XlsxFormatProvider also has an overload of the Export() method which accepts a Stream object as a second parameter and writes the data in it - XlsxFormatProvider API Reference
You can take a look at the example with a FileStream in this help article
and adapt it to your exact needs.
I hope this helps.
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Feedback Portal
and vote to affect the priority of the items