How to generate PDF in NET core using iText7 library

I'm using NET Core 6 and I'm playing with the PDF documents or to be more precise how to create PDF documents using iText7 nuget library but it seems that I'm doing something wrong here since I'm getting this response in swagger:

And simple sample of the code for generating PDF is this:

 private static byte[] CreateInvoiceDocument()
        {
            using var memoryStream = new MemoryStream();

            var writer = new PdfWriter(memoryStream);
            var pdf = new PdfDocument(writer);
            pdf.SetDefaultPageSize(PageSize.A4);
            var document = new Document(pdf);
            // Header table
            var headerTable = new Table(1);
            headerTable.SetWidth(UnitValue.CreatePercentValue(100));

            var test = new Paragraph("dwawwa");

            var headerCell = new Cell().Add(new Paragraph("Invoice"));
            headerCell.SetTextAlignment(TextAlignment.CENTER);
            headerTable.AddCell(headerCell);

            document.Add(headerTable);

            // Invoice details table
            var detailsTable = new Table(2);
            detailsTable.SetWidth(UnitValue.CreatePercentValue(100));
            detailsTable.SetMarginTop(20);

            detailsTable.AddCell("Invoice Number");
            detailsTable.AddCell("12");

            detailsTable.AddCell("Date");
            detailsTable.AddCell(DateTime.Now.ToString("dd/MM/yyyy"));

            // Add more details as needed

            document.Add(detailsTable);

            // Footer
            var footerTable = new Table(1);
            footerTable.SetWidth(UnitValue.CreatePercentValue(100));
            footerTable.SetMarginTop(20);

            var footerCell = new Cell().Add(new Paragraph("Thank you for your business!"));
            footerCell.SetTextAlignment(TextAlignment.CENTER);
            footerTable.AddCell(footerCell);

            document.Add(footerTable);

            document.Close();

            return memoryStream.ToArray();
        }

And this should be API response:

public async Task<IActionResult> GetInvoicePDF()
{
    var response = CreateInvoiceDocument();

    if (response == null)
        return BadRequest("Failed to generate the PDF.");

    var stream = new MemoryStream(response);
    return new FileStreamResult(stream, "application/pdf");
}

Please, what I'm doing wrong nad thank you in advance.

Try to use FileContentResult which inherits from IActionResult but helps Swagger to recognize it as a file in SwaggerUI.

public async Task<FileContentResult> GetInvoicePDF()
{
 var response = CreateInvoiceDocument();

 if (response == null)
    return BadRequest("Failed to generate the PDF.");

 var stream = new MemoryStream(response);
 FileContentResult file = new FileContentResult(stream.ToArray(), "application/pdf")
 {
   FileDownloadName = Path.GetFileName("yourfilename.pdf")
 };

 return file;
}

Ok, after a while I finally figure it out.After adding MediaTypeNames.Application.Pdf into FileContentResult everything work as expected.
Thank you all and hope that code below will help you in the future

public async Task<FileContentResult> GetInvoicePDF()
{
    var response = CreateInvoiceDocument();

    if (response == null)
        return BadRequest("Failed to generate the PDF.");

    var stream = new MemoryStream(response);
    var result = new FileContentResult(response, MediaTypeNames.Application.Pdf)
    {
        FileDownloadName = "test.pdf"
    };

    return result;
}