Convert Excel to PDF with Azure function in .NET standard application.

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

[FunctionName("Function1")]
public static async Task<HttpResponseMessage> Run([HttpTrigger(AuthorizationLevel.Function, "get", "post", Route = null)] HttpRequestMessage req, TraceWriter log)
{
    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;
        // Assign default application version
        application.DefaultVersion = ExcelVersion.Excel2013;
        IWorkbook workbook = application.Workbooks.Open(stream);
        // Access a worksheet from the workbook
        IWorksheet worksheet = workbook.Worksheets[0];
        // Open the Excel document to convert
        XlsIORenderer renderer = new XlsIORenderer();
        // Initialize PDF document
        PdfDocument pdfDocument = new PdfDocument();
        // Convert Excel document into PDF document
        pdfDocument = renderer.ConvertToPDF(workbook);
        MemoryStream memoryStream = new MemoryStream();
        // Save the PDF file
        pdfDocument.Save(memoryStream);
        // Create the response to return
        HttpResponseMessage response = new HttpResponseMessage(HttpStatusCode.OK);
        // Set the PDF document content response
        response.Content = new ByteArrayContent(memoryStream.ToArray());
        // Set the content disposition as attachment
        response.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment")
        {
            FileName = "Output.pdf"
        };
        // Set the content type as PDF format MIME type
        response.Content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("application/pdf");
        // Return the response with output PDF stream
        return response;
    }
}

// Open the required template Excel file
Stream fileStream = File.Open("../../Data/Input.xlsx", FileMode.Open);
// Create a memory stream to save the template
MemoryStream inputStream = new MemoryStream();
// Copy the file stream into memory stream
fileStream.CopyTo(inputStream);
// Dispose of 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 store the Excel document stream
    Stream stream = req.GetRequestStream();
    // Write the Excel document stream into the request stream
    stream.Write(inputStream.ToArray(), 0, inputStream.ToArray().Length);
    // Get the response from the Azure Function request
    HttpWebResponse res = (HttpWebResponse)req.GetResponse();
    // Create file stream to save the output PDF file
    FileStream outStream = File.Create("Sample.pdf");
    // Copy the response stream into the file stream
    res.GetResponseStream().CopyTo(outStream);
    // Dispose of the input stream
    inputStream.Dispose();
    // Dispose of the file stream
    outStream.Dispose();
}
catch (Exception ex)
{
    throw;
}
// Launch the output document
System.Diagnostics.Process.Start("Sample.pdf");