Hi Franck,
On seeing your query it seems that you are using the Essential DocIO version older than 5.2. If so, then you have to use the following code to add a table.
//Adding a paragraph to the section.
IWParagraph paragraph = section.AddParagraph();
ITable table = paragraph.AppendTable();
In the latest version (5.2) we have improved our current object model for better usability and functionality, however there are some breaking changes in APIs. We have moved the table from Paragraph to Body. Please refer to this document for a detailed list of changes:
http://www.syncfusion.com/Product/uploads/DocIO APIchanges_f9afbe8a.pdfLet us know if you need any further information.
Regards,
Saravanan