This is a sample code to replicate the error which is triggered on export:
string inputFileName = "input.xlsx";
if (!File.Exists(inputFileName))
{
throw new FileNotFoundException(String.Format("File {0} was not found!", inputFileName));
}
Telerik.Windows.Documents.Spreadsheet.Model.Workbook workbook;
IWorkbookFormatProvider formatProvider = new Telerik.Windows.Documents.Spreadsheet.FormatProviders.OpenXml.Xlsx.XlsxFormatProvider();
using (Stream input = new FileStream(inputFileName, FileMode.Open))
{
workbook = formatProvider.Import(input, TimeSpan.MaxValue);
}
string outputFilePath = "output.xlsx";
using (Stream output = new FileStream(outputFilePath, FileMode.Create))
{
formatProvider.Export(workbook, output, TimeSpan.MaxValue);
}
Process.Start(new ProcessStartInfo() { FileName = outputFilePath, UseShellExecute = true });