Thank you for considering Aspose.
You will not achieve proper results in this way because you are trying to insert a section break into a table cell. If you need to insert the break to a paragraph right after the table, the following approach could probably be better:
Table table = doc.Sections[sectionIndex].Body.Tables[tableIndex];<?xml:namespace prefix = o ns = “urn:schemas-microsoft-com:office:office” /><o:p></o:p>
Paragraph paraAfterTable = (Paragraph)table.NextSibling;<o:p></o:p>
//Try this one too.
//Paragraph paraAfterTable = (Paragraph)table.NextSibling.NextSibling;<o:p></o:p>
DocumentBuilder builder = new DocumentBuilder(doc);
<o:p>Note that the section break is invisible, but if you put the cursor in the paragraph below the table you will see in the status bar in MS Word it shows the cursor is in the 2nd section.<o:p></o:p>
This seem to be just some strange MS Word behaviour to treat a section break that is immediately after a table in this way. If you want to insert the section break in a more “normal” MS Word-like way, then uncomment the line of code that inserts the break after the paragraph that is after the table.<o:p></o:p>