protected void RadGrid1_InfrastructureExporting(object sender, GridInfrastructureExportingEventArgs e)
{
    ExportStructure.ExportStructure structure = e.ExportStructure;
 
    // Render the structure to XLSX format and return it to a byte array
    ExportStructure.XlsxRenderer renderer = new ExportStructure.XlsxRenderer(structure);
    byte[] xlsxByteArray = renderer.Render();
 
    // create an format provider instance
    XLSX.XlsxFormatProvider formatProvider = new XLSX.XlsxFormatProvider();
    // import the newly created document into a Workbook
    WB.Workbook myWorkbook = formatProvider.Import(xlsxByteArray);
 
    myWorkbook.Worksheets[0].Name = "MySheet";
 
    // once finished with changes convert the workbook back to byte array
    byte[] data = formatProvider.Export(myWorkbook);
 
    // return the byte array for downloading.
    Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
    Response.Headers.Remove("Content-Disposition");
    Response.AppendHeader("Content-Disposition", string.Format("attachment; filename={0}.xlsx", RadGrid1.ExportSettings.FileName));
    Response.BinaryWrite(data);
    Response.End();
}