iText7 Table of Content

I am new to iText7, but have a decent grasp of most of the concepts.

I would like to create a table of content (TOC) for my PDF, and found the following java example on their website: https://developers.itextpdf.com/content/itext-7-examples/itext-7-bookmarks-tocs/toc-first-page

Converting the program to c# has worked out with normal text, but when having the Paragraphs inside Cells in a table, it doesn't work anymore.

~~Furthermore i can't get the Reorder pages part to work, any ideas?~~

EDIT: Found a way to reorder the pages

using iText.IO.Font.Constants;
using iText.IO.Source;
using iText.Kernel.Font;
using iText.Kernel.Pdf;
using iText.Kernel.Pdf.Action;
using iText.Kernel.Pdf.Canvas.Draw;
using iText.Kernel.Pdf.Navigation;
using iText.Layout;
using iText.Layout.Element;
using iText.Layout.Hyphenation;
using iText.Layout.Layout;
using iText.Layout.Properties;
using iText.Layout.Renderer;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;

namespace ConsoleApp2
{
    class Program
    {
        public const string Src = @"C:\Users\mgs\source\repos\ConsoleApp2\text.txt";
        public const string Dest = @"C:\Users\mgs\source\repos\ConsoleApp2\table_of_contents.pdf";

        static void Main(string[] args)
        {
            byte[] bytes = CreatePdf();

            File.WriteAllBytes(Dest, bytes);
        }


        public static byte[] CreatePdf()
        {
            using (var s = new MemoryStream())
            {
                PdfDocument pdf = new PdfDocument(new PdfWriter(s));
                pdf.GetCatalog().SetPageMode(PdfName.UseOutlines);

                PdfFont font = PdfFontFactory.CreateFont(StandardFonts.TIMES_ROMAN);
                PdfFont bold = PdfFontFactory.CreateFont(StandardFonts.HELVETICA_BOLD);
                Document document = new Document(pdf);
                document.SetTextAlignment(TextAlignment.JUSTIFIED)
                        .SetHyphenation(new HyphenationConfig("en", "uk", 3, 3))
                        .SetFont(font)
                        .SetFontSize(11);

                // parse text to PDF
                Dictionary<string, KeyValuePair<string, int>> toc = WritePdf(pdf, bold, document);

                document.Add(new AreaBreak(AreaBreakType.NEXT_PAGE));

                // create table of contents
                int startToc = CreateToc(pdf, bold, document, toc);

                int tocPages = pdf.GetNumberOfPages() - startToc;

                document.Close();

                PdfDocument srcDoc = new PdfDocument(new PdfReader(new RandomAccessSourceFactory().CreateSource(s.ToArray()), new ReaderProperties()));

                using (MemoryStream ms = new MemoryStream())
                {
                    PdfDocument resultDoc = new PdfDocument(new PdfWriter(ms));
                    resultDoc.InitializeOutlines();


                    var pages = ReorderPages(tocPages, srcDoc, startToc);


                    srcDoc.CopyPagesTo(pages, resultDoc);

                    resultDoc.Close();
                    srcDoc.Close();

                    byte[] bytes = ms.ToArray();
                    return bytes;

                }
            }
        }

        private static List<int> ReorderPages(int tocPages, PdfDocument pdf, int startToc)
        {
            int allpages = pdf.GetNumberOfPages();

            var pages = new List<int>();
            for (var i = 0; i <= tocPages; i++)
            {
                pages.Add(startToc + i);
            }

            for (var i = 0; i < allpages - (tocPages + 1); i++)
            {
                pages.Add(i + 1);
            }

            return pages;
        }

        private static int CreateToc(PdfDocument pdf, PdfFont bold, Document document, Dictionary<string, KeyValuePair<string, int>> toc)
        {
            int startToc = pdf.GetNumberOfPages();
            var p = new Paragraph()
                .SetFont(bold)
                .Add("Table of Contents")
                .SetDestination("toc");

            document.Add(p);

            toc.Remove(toc.First().Key);
            List<TabStop> tabstops = new List<TabStop>();
            tabstops.Add(new TabStop(580, TabAlignment.RIGHT, new DottedLine()));

            foreach (KeyValuePair<string, KeyValuePair<string, int>> entry in toc)
            {
                KeyValuePair<string, int> text = entry.Value;
                string entryKey = entry.Key;
                string textKey = text.Key;
                string textValue = text.Value.ToString();

                p = new Paragraph()
                    .AddTabStops(tabstops)
                    .Add(textKey)
                    .Add(new Tab())
                    .Add(textValue)
                    .SetAction(PdfAction.CreateGoTo(entryKey));

                document.Add(p);
            }

            return startToc;
        }

        private static Dictionary<string, KeyValuePair<string, int>> WritePdf(PdfDocument pdf, PdfFont bold, Document document)
        {
            string[] lines = File.ReadAllLines(Src);
            var title = true;
            var counter = 0;
            PdfOutline outline = null;
            var toc = new Dictionary<string, KeyValuePair<string, int>>();

            var t = new Table(1);

            foreach (string line in lines)
            {
                var p = new Paragraph(line);
                p.SetKeepTogether(true);
                if (title)
                {
                    string name = "title" + counter++;
                    outline = CreateOutline(outline, pdf, line, name);

                    KeyValuePair<string, int> titlePage = new KeyValuePair<string, int>(line, pdf.GetNumberOfPages());
                    p.SetFont(bold)
                        .SetFontSize(12)
                        .SetKeepWithNext(true)
                        .SetDestination(name)
                        .SetNextRenderer(new UpdatePageRenderer(p, titlePage));

                    title = false;

                    //TODO: 
                    var c = new Cell().Add(p);
                    t.AddCell(c);

                    //document.Add(p);

                    toc.Add(name, titlePage);
                }
                else
                {
                    p.SetFirstLineIndent(36);
                    if (string.IsNullOrWhiteSpace(line))
                    {
                        p.SetMarginBottom(12);
                        title = true;
                    }
                    else
                    {
                        p.SetMarginBottom(0);
                    }

                    //TODO: 
                    var c = new Cell().Add(p);
                    t.AddCell(c);

                    //document.Add(p);
                }
            }

            //TODO: 
            document.Add(t);

            return toc;
        }

        protected class UpdatePageRenderer : ParagraphRenderer
        {
            protected KeyValuePair<string, int> Entry;

            public UpdatePageRenderer(Paragraph modelElement, KeyValuePair<string, int> entry) : base(modelElement)
            {
                Entry = entry;
            }

            public override LayoutResult Layout(LayoutContext layoutContext)
            {
                var result = base.Layout(layoutContext);
                int pageNumber = layoutContext.GetArea().GetPageNumber();

                Entry = new KeyValuePair<string, int>(Entry.Key, pageNumber);
                return result;
            }
        }

        public static PdfOutline CreateOutline(PdfOutline outline, PdfDocument pdf, String title, String name)
        {
            if (outline == null)
            {
                outline = pdf.GetOutlines(false);
                outline = outline.AddOutline(title);
                outline.AddDestination(PdfDestination.MakeDestination(new PdfString(name)));
                return outline;
            }
            var kid = outline.AddOutline(title);
            kid.AddDestination(PdfDestination.MakeDestination(newPdfString(name)));
            return outline;
        }
    }
}

The reason why all the page numbers are 0 is because you aren't adding any content before attempting to get the page numbers.

Highlighting the important parts of your WritePdf() function:

private static Dictionary < string, KeyValuePair < string, int >> WritePdf(PdfDocument pdf, PdfFont bold, Document document) {

  ...
  var t = new Table(1);

  ...
  foreach (string line in lines) {
   //Adding content to the table and getting the page numbers. 
    //Content is *not* added to the document yet, so pdf.GetNumberOfPages() returns 0
  }

  ...
  document.add(t); //Finally adding the table to the document after it is too late

}

You can alter the approach a bit by adding the table to the document first and then periodically flushing it like so:

private static Dictionary < string, KeyValuePair < string, int >> WritePdf(PdfDocument pdf, PdfFont bold, Document document) {

  ...
  var t = new Table(1, true); //True stands for "large table" which allows us to flush the content.
  document.Add(t); //Immediately add the document to the table

  ...
  foreach (string line in lines) {

    //Add whatever you want to the table

    t.flush(); //But make sure to flush the content so the page numbers are correct
  }

  ...
  t.complete() //Tell the renderer that the table will not have any more content added to it.

}

This would be your updated function:

private static Dictionary<string, KeyValuePair<string, int>> WritePdf(PdfDocument pdf, PdfFont bold, Document document)
    {
        string[] lines = File.ReadAllLines(SRC);
        var title = true;
        var counter = 0;
        PdfOutline outline = null;
        var toc = new Dictionary<string, KeyValuePair<string, int>>();

        var t = new Table(1, true);

        document.Add(t);

            foreach (string line in lines) {
            var p = new Paragraph(line);
            p.SetKeepTogether(true);
            if (title) {
                string name = "title" + counter++;
                outline = CreateOutline(outline, pdf, line, name);

                KeyValuePair<string, int> titlePage = new KeyValuePair<string, int>(line, pdf.GetNumberOfPages());
                p.SetFont(bold)
                    .SetFontSize(12)
                    .SetKeepWithNext(true)
                    .SetDestination(name)
                    .SetNextRenderer(new UpdatePageRenderer(p, titlePage));

                title = false;

                //TODO: 

                //document.Add(p);

                toc.Add(name, titlePage);
            }
            else {
                p.SetFirstLineIndent(36);
                if (string.IsNullOrWhiteSpace(line)) {
                    p.SetMarginBottom(12);
                    title = true;
                }
                else {
                    p.SetMarginBottom(0);
                }

                //TODO: 
                var c = new Cell().Add(p);
                t.AddCell(c);

                //document.Add(p);
            }
                t.Flush();
        }
            t.Complete();

        //TODO: 


        return toc;
    }

Which appears to correctly input the page numbers