Cannot convert workbook to sheet in NPOI

Question

I use NPOI 2.0.1 beta to import excel(xlsx) data to GridView .
Firstly , using this link , convert xlsx Worksheet format to xls Worksheet .
But , at the following line , it's show me error .

 HSSFWorkbook workbook = new HSSFWorkbook();
 MemoryStream memoryStream = new MemoryStream();
 HSSFSheet sheet = workbook.CreateSheet("Sheet1");
 HSSFRow headerRow = sheet.CreateRow(0);

And here is a screen-shoot ,

How can I fix it ?
Or is there a better way ? Thanks In Advance :)

Answer 1

In NPOI 2.0, you should use ISheet and IWorkbook interface.

ISheet sheet = workbook.CreateSheet("Sheet1");