Convert xls to xlsx with C#

Sample code:

 

Microsoft.Office.Interop.Excel.

Application oExcel = new Application();
object oMissing = Type.Missing;
string fileName = @"D:\Test\WorksheetNamesExpected.xls";
Workbook _book = oExcel.Workbooks.Open(fileName, oMissing, oMissing, oMissing, oMissing, oMissing, oMissing, oMissing, oMissing, oMissing, oMissing, oMissing, oMissing, oMissing, oMissing);
object fileName2 = @"D:\Test\WorksheetNamesExpected.xlsx";
object fileFormat = XlFileFormat.xlOpenXMLWorkbook;
_book.SaveAs(fileName2, fileFormat, oMissing, oMissing, oMissing, oMissing,

XlSaveAsAccessMode.xlNoChange, oMissing, oMissing, oMissing, oMissing, oMissing);
_book.Close();