Paragraphs expose a property called OutlineLevel that determines the level of the paragraph's text when placed in a table of contents. The default value of this property is BodyText, which means that the paragraph will not be included in the table of contents. If you change the value of the property to a value from Level1 to Level9, then the paragraph's text will be included in the table of contents.

In most cases, you will not change the outline level of the paragraph but rather apply one of the heading styles (e.g. "Heading1") to it. The heading styles set the OutlineLevel of the paragraphs they are applied to through styling. The following code example demonstrates how to apply a heading style to a paragraph:

// Get a reference to the "Heading1" style
NRichTextStyle heading1Style = richTextView.Content.Styles.GetStyleByTypeAndName(ENRichTextStyleType.Paragraph, "Heading1");

// Create and style a paragraph
Paragraph paragraph = new NParagraph("Chapter 1");
section.Blocks.Add(paragraph);
heading1Style.Apply(paragraph);

After the "Heading1" style is applied to the paragraph, it will have an outline level of 1 and will be included in the table of contents.

To add a table of contents to a rich text document, simply create an NTableOfContentsBlock and add it to the document.

NTableOfContentsBlock tableOfContents = new NTableOfContentsBlock();
section.Blocks.Add(tableOfContents);

When you want to update the table of contents, simply call its Update method. Note that if the rich text view's document is not yet evaluated, you should call the Evaluate method of the rich text view document first.

richTextView.Document.Evaluate();
tableOfContents.Update();

By default the table of contents block's title is "Table of Contents". If you want to change that default title you should create and add a paragraph to the table of content's collection of blocks or simply use the AddTitleParagraph method as shown in the following code snippet:

NTableOfContentsBlock tableOfContents = new NTableOfContentsBlock();
section.Blocks.Add(tableOfContents);
tableOfContents.AddTitleParagraph("My Cutsom Title");

The table of contents block also relies on the "TOCHeading" of the table of contents title and from the "TOC1" to the "TOC9" styles for the table of contents entries. You can modify any of these styles if you want to change the appearance of your table of contents. The following code example demonstrates how to make the title of a table of contents red and the first level table of content entries - blue:

NParagraphStyle tocHeadingStyle = (NParagraphStyle)documentBlock.Styles.GetStyleByTypeAndName(
    ENRichTextStyleType.Paragraph, "TOCHeading");
tocHeadingStyle.InlineRule.Fill = new NColorFill(NColor.Red);

NParagraphStyle toc1Style = (NParagraphStyle)documentBlock.Styles.GetStyleByTypeAndName(
    ENRichTextStyleType.Paragraph, "TOC1");
toc1Style.InlineRule.Fill = new NColorFill(NColor.Blue);

Styles