huge data export in pdf itextsharp

Question

I try to export data in PDF there is huge data so when i export ..here i dont export data from gridview but actually here i create dummy gridview in code and bind data in that grid.. i am not displaying the data the grid in page .. I try below code

    Private Sub ExportGridToPDF()
        Using myMemoryStream As New MemoryStream()

            Dim myDocument As New iTextSharp.text.Document(iTextSharp.text.PageSize.A1, 10.0F, 10.0F, 10.0F, 0.0F)
            ' Dim myDocument As New iTextSharp.text.Document()
            Dim myPDFWriter As PdfWriter = PdfWriter.GetInstance(myDocument, myMemoryStream)

            myDocument.Open()

            ' Add to content to your PDF here...

            Dim sw As New StringWriter()
            Dim hw As New HtmlTextWriter(sw)
            GridView1.AllowPaging = False
            GridView1.DataBind()
            GridView1.RenderControl(hw)
            ' We're done adding stuff to our PDF.
            myDocument.Add(hw)
            myDocument.Close()

            Dim content As Byte() = myMemoryStream.ToArray()

            ' Write out PDF from memory stream.
            Using fs As FileStream = File.Create("eport_PDF.pdf")
                fs.Write(content, 0, CInt(content.Length))
            End Using
        End Using
End Sub

when i run this shows an error

System.InvalidCastException: Unable to cast object of type 'System.Web.UI.HtmlTextWriter' to type 'iTextSharp.text.IElement'.

on this line myDocument.Add(hw)

I use memory stream because of huge data when i use code without memory stream then shows an error Out of Memory exception so i use memory stream and now this shows different error

Answer 1

The Add() method in the Document object only accepts parameters that implement the IElement interface. You are passing an HtmlTextWriter object. That object is totally unrelated to iText. It is truly amazing that you would think this could work.

In this question, as in previous questions you posted (some of which are deleted), you refer to HTML. You were using HTMLWorker in Add image using itextsharp and the deleted question Out Of Memory Exception error itext sharp.

If you want to convert HTML to PDF, you should upgrade to iText 7 and use the pdfHTML add-on. Take a look at the tutorial to see how HTML to PDF conversion is done: https://developers.itextpdf.com/content/itext-7-converting-html-pdf-pdfhtml

In a comment to this answer however, you write: I'm not exporting data in HTML to PDF. OK, if that's true, then why do you refer to HTML in your code? That's very confusing.

Furthermore, you write I create dummy grid-view in code and bind data in it. Unfortunately, you don't give us any information about the format of that dummy grid-view. I assume, it's something you "invented" yourself, but if that's the case, how do you suppose that iText can magically understand the dummy grid-view you invented?

I started this answer by saying the the Add() method only accepts objects that implement the IElement interface. Since you are talking about a grid, it's probably interesting to use an iText table element. In iText 5, there's an object named PdfPTable; in iText 7, that object is simply named Table.

Many people with large data sets, create such a table object first, then add it to a Document. That's not always wise, because objects keep building up in memory, eventually resulting in an OutOfMemoryException. For large data sets, you should mark the table as a large element, and add the table gradually.

In iText 5, the code would look like this:

Document document = new Document();
FileStream stream = new FileStream(fileName, FileMode.Create);
var pdfWriter = PdfWriter.GetInstance(document, stream);
document.Open();
PdfPTable table = new PdfPTable(4);
table.Complete = false;
for (int i = 0; i < 1000000; i++) {
    PdfPCell cell = new PdfPCell(new Phrase(i.ToString()));
    table.AddCell(cell);
    if (i > 0 && i % 1000 == 0) {
        document.Add(table);
    }
}
table.Complete = true;
document.Add(table);
document.Close();

We're adding 1000000 cells to a table with 4 columns, but we add the table every 1000 cells (so every 250 rows). This means that the content is flushed from memory on a regular basis, thus avoiding an OutOfMemoryException.

Since you seem to be new at iText, do yourself a favor, and upgrade to using iText 7. iText 5 is in maintenance mode, which means that no new functionality will be added to that version. For instance: if at some point someone asks you to produce PDF 2.0 files (the PDF 2.0 spec was released a couple of months ago), you will have to throw all your iText 5 code away, and start anew, because only iText 7 will support PDF 2.0.

The large table functionality in iText 7, is discussed at the end of chapter 5 of the tutorial:

PdfDocument pdf = new PdfDocument(new PdfWriter(dest));
Document document = new Document(pdf);
Table table = new Table(new[] {1f, 1f, 1f}, true);
table.AddHeaderCell("Table header 1");
table.AddHeaderCell("Table header 2");
table.AddHeaderCell("Table header 3");
table.AddFooterCell("Table footer 1");
table.AddFooterCell("Table footer 2");
table.AddFooterCell("Table footer 3");
document.Add(table);
for (int i = 0; i < 1000; i++)
{
    table.AddCell($"Row {i + 1}; column 1");
    table.AddCell($"Row {i + 1}; column 2");
    table.AddCell($"Row {i + 1}; column 3");
    if (i % 50 == 0)
    {
        table.Flush();
    }
 }
 table.Complete();
 document.Close();

As you can see, the iText 7 code is much more intuitive. We create a table with 3 columns, and the second parameter (true) indicates that we will add a very large table. We add a header, we add a footer, and we add the table to the document. Then we add 1000 rows, but we Flush() the table every 50 rows. Flushing free memory, avoiding going out of memory. Once we're done, we Complete() the table.

All of this is documented on the official web site! There is no need for you to invent your own grid view. As you have found out, inventing your own grid view cannot possibly work.

Also important: you say iTextSharp, I say iText. We both mean the same thing: the PDF library produced by iText Group that can be used to create PDF documents from C# code. Only you are using the old name, whereas we try to avoid that name based on the advice of a Trademark who told us that there's a company named Sharp that doesn't appreciate other companies using the word Sharp in the context of brands that aren't related to their company. So please stop saying that you're using iTextSharp; you're using iText!