How to export the WinForms GridControl to excel with extension .xlsx?

private void exportBtn_Click(object sender, EventArgs e)
{
    //support to export the grid to excel
    GridExcelConverterControl converter = new GridExcelConverterControl();
    ExcelEngine excelEngine = new ExcelEngine();
    IApplication application = excelEngine.Excel;
    application.DefaultVersion = ExcelVersion.Excel2007;
    IWorkbook workBook = ExcelUtils.CreateWorkbook(1);
    workBook.Version = ExcelVersion.Excel2007;
    IWorksheet sheet = workBook.Worksheets[0]; 
    //used to convert grid to excel
    converter.GridToExcel(this.gridControl1, sheet, ConverterOptions.Default);
    //used to save the file
    workBook.SaveAs("sample.xlsx");
    //used to open the file
    Process.Start("sample.xlsx");
}

Private Sub exportBtn_Click(ByVal sender As Object, ByVal e As EventArgs)
  'support to export the grid to excel
  Dim converter As New GridExcelConverterControl()
  Dim excelEngine As New ExcelEngine()
  Dim application As IApplication = excelEngine.Excel
  application.DefaultVersion = ExcelVersion.Excel2007
  Dim workBook As IWorkbook = ExcelUtils.CreateWorkbook(1)
  workBook.Version = ExcelVersion.Excel2007
  Dim sheet As IWorksheet = workBook.Worksheets(0)
  'used to convert grid to excel
  converter.GridToExcel(Me.gridControl1, sheet, ConverterOptions.Default)
  'used to save the file
  workBook.SaveAs("sample.xlsx")
  'used to open the file
  Process.Start("sample.xlsx")
End Sub