Chart not save into xlsx file

[NPR18041]

I am created line chart follow this code Line Chart

and save to xlsx file WorkBook.Save(pathFile, FileFormat.Excel2007);

program display

excel file display

Question: Why this line chart is not save into excel file?

[abstractspoon]

Additional Example:

Loading the attached Excel 2007 file into the Window Forms Editor and resaving to Excel 2007 loses the chart chart.xlsx .