How to merge multiple CSV files into single Excel workbook

using (ExcelEngine excelEngine = new ExcelEngine())
{
        IApplication application = excelEngine.Excel;
        application.DefaultVersion = ExcelVersion.Excel2016;
 
        string[] CSVFiles = new string[] { "CSVFile1", "CSVFile2", "CSVFile3" };
 
        IWorkbook workbook = application.Workbooks.Create(1);
 
        for (int i = 0; i < CSVFiles.Length; i++)
        {
        FileStream inputStream = new FileStream(CSVFiles[i] + ".csv", FileMode.Open, FileAccess.Read);
        IWorkbook CSVWorkbook = application.Workbooks.Open(inputStream);
        workbook.Worksheets.AddCopy(CSVWorkbook.Worksheets);
        }
 
        workbook.Worksheets[0].Remove();
 
        //Saving the Excel to the MemoryStream 
        MemoryStream stream = new MemoryStream();
        workbook.SaveAs(stream);
 
        //Set the position as '0'.
        stream.Position = 0;
 
        //Download the Excel file in the browser
        FileStreamResult fileStreamResult = new FileStreamResult(stream, "application/excel");
        fileStreamResult.FileDownloadName = "Output.xlsx";
        return fileStreamResult;
}