Error When Export xlsx with RadDocument

[Hung]

var workbook = CreateWorkBook(grid, settings);

                     if (workbook != null)
                     {
                         var provider = new XlsxFormatProvider();
                         using (var output = dialog.OpenFile())
                         {
                             provider.Export(workbook, output);
                             fileName = dialog.FileName;
                         }
                     }

I use your demo for my project. But some time I get Error : the writer is closed or in error state.
Any Idea about this error.
It happen  in line: provider.Export(workbook, output);
Thanks

[Petya]

Hello Hung,

It is hard to say what might be causing this error based on the provided information. Could you elaborate on your scenario, please? Does this issue occur regardless of the contents in the RadGridView or is it reproducible in specific circumstances? Also, could you please send us the full stack trace of the exception?

Any additional information you feel is relevant would also be appreciated. We're looking forward to hearing from you.

Regards,
Petya
Telerik