iTextSharp.text.pdf.PdfWriter.GetInstance C# (CSharp) Méthode

        public static PdfWriter GetInstance(Document document, Stream os)
        {
            PdfDocument pdf = new PdfDocument();
            document.AddDocListener(pdf);
            PdfWriter writer = new PdfWriter(pdf, os);
            pdf.AddWriter(writer);
            return writer;
        }

        protected void BtnSavePDF_Click(object sender, EventArgs e)
        {
            Document pdfDoc = new Document(PageSize.A4, 10f, 10f, 10f, 0f);

            PdfWriter.GetInstance(pdfDoc, Response.OutputStream);
            pdfDoc.Open();
            using (MemoryStream stream = new MemoryStream())
            {
                Alumnos.SaveImage(stream, ChartImageFormat.Png);
                iTextSharp.text.Image chartImage = iTextSharp.text.Image.GetInstance(stream.GetBuffer());
                chartImage.ScalePercent(75f);
                pdfDoc.Add(chartImage);
                pdfDoc.Close();

                Response.ContentType = "application/pdf";
                Response.AddHeader("content-disposition", "attachment;filename=Chart.pdf");
                Response.Cache.SetCacheability(HttpCacheability.NoCache);
                Response.Write(pdfDoc);
                Response.End();
            }
        }