How to create Excel file in Azure functions?

using System.IO;
using Syncfusion.XlsIO;
using System.Net.Http.Headers;

Stream stream = req.Content.ReadAsStreamAsync().Result;
//Instantiate the spreadsheet creation engine
using (ExcelEngine excelEngine = new ExcelEngine())
{
    //Instantiate the Excel application object
    IApplication application = excelEngine.Excel;
 
    //Assigns default application version
    application.DefaultVersion = ExcelVersion.Excel2013;
 
    //A new workbook is created equivalent to creating a new workbook in Excel
    //Create a workbook with 1 worksheet
IWorkbook workbook = application.Workbooks. Open(stream); 
 
    //Access a worksheet from workbook
    IWorksheet worksheet = workbook.Worksheets[0];
 
    //Adding text data
    worksheet.Range["A1"].Text = "Month";
    worksheet.Range["B1"].Text = "Sales";
    worksheet.Range["A6"].Text = "Total";
 
    //Adding DateTime data
    worksheet.Range["A2"].DateTime = new DateTime(2015, 1, 10);
    worksheet.Range["A3"].DateTime = new DateTime(2015, 2, 10);
    worksheet.Range["A4"].DateTime = new DateTime(2015, 3, 10);
 
    //Applying number format for date value cells A2 to A4
    worksheet.Range["A2:A4"].NumberFormat = "mmmm, yyyy";
 
    //Auto-size the first column to fit the content
    worksheet.AutofitColumn(1);
 
    //Adding numeric data
    worksheet.Range["B2"].Number = 68878;
    worksheet.Range["B3"].Number = 71550;
    worksheet.Range["B4"].Number = 72808;
 
    //Adding formula
    worksheet.Range["B6"].Formula = "SUM(B2:B4)";
 
    MemoryStream memorystream = new MemoryStream();
 
    //Saving the workbook to stream in XLSX format
    workbook.Version = ExcelVersion.Excel2013;
    workbook.SaveAs(memorystream);
 
    //Create the response to return
    HttpResponseMessage response = new HttpResponseMessage(HttpStatusCode.OK);
 
    //Set the Excel document content response
    response.Content = new ByteArrayContent(memorystream.ToArray());
 
    //Set the contentDisposition as attachment
    response.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment")
    {
        FileName = "Output.xlsx"
    };
    //Set the content type as xlsx format mime type
    response.Content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("application/vnd.openxmlformats-officedocument.spreadsheet.excel");
    //Return the response with output Excel stream
    return response;
}

   //Open the required template Excel file
    Stream fileStream = File.Open(@"../../Data/Input.xlsx", FileMode.Open);
 
    //Create memory stream to save the template
    MemoryStream inputStream = new MemoryStream();
 
    //Copy the file stream into memory stream
    fileStream.CopyTo(inputStream);
 
    //Dispose the file stream
    fileStream.Dispose();
    try
    {
        //Create HttpWebRequest with hosted azure function URL
        HttpWebRequest req = (HttpWebRequest)WebRequest.Create(" Your Azure Function Url");
 
        //Set request method as POST
        req.Method = "POST";
 
        //Get the request stream to strore the Excel document stream
        Stream stream = req.GetRequestStream();
 
        //Write the Excel document stream into request stream
        stream.Write(inputStream.ToArray(), 0, inputStream.ToArray().Length);
 
        //Gets the responce from the Azure Function request.
        HttpWebResponse res = (HttpWebResponse)req.GetResponse();
 
        //Create file stream to save the output Excel file
        FileStream outStream = File.Create("Sample.xlsx");
 
        //Copy the responce stream into file stream
        res.GetResponseStream().CopyTo(outStream);
 
        //Dispose the input stream
        inputStream.Dispose();
 
        //Dispose the file stream
        outStream.Dispose();
    }
    catch (Exception ex)
    {
        throw;
    }
 
    //Launch the output document
    System.Diagnostics.Process.Start("Sample.xlsx");
}