How to convert xls file to xlsm in c#

Question

I am working with ClosedXML utility for excel operations. It only supports files created on office versions 2007 on-words. I have an xls file and required to convert to xlms(macro enabled). Simple copy as shown below is not working.

string oldFile = @"C:\Files\xls.xls";
string newFile = @"C:\Files\xlsnew.xlsm";

File.Copy(xls_file,xlsm_file);

And I have used below code also

    byte[] byteArray = File.ReadAllBytes(oldFile);
    using (MemoryStream stream = new MemoryStream())
    {
        stream.Write(byteArray, 0, (int)byteArray.Length);
        using (SpreadsheetDocument spreadsheetDoc = SpreadsheetDocument.Open(stream, true))
        {
            // Change from template type to workbook type
            spreadsheetDoc.ChangeDocumentType(SpreadsheetDocumentType.MacroEnabledWorkbook);
        }
        File.WriteAllBytes(newFile, stream.ToArray());
    }

Please provide a helpful solution.

Thanks in advance.