I need to format the table of contents (TOC) in multiple Word documents daily. I'm using Power Automate with OpenXML (C#) to add the TOC. However, the code is inserting a TOC but not update it automatically, as shown in the attached image.

The main requirement is:

1. If a TOC already exists, it should be updated.

2. If no TOC is present, it should be inserted.

Note: The solution must work online only.

Is there any other approach to achieve this?

private static void GenerateTableOfContents(Body body)
{
     var tocParagraph = new Paragraph(new Run(new Text("Table of Contents")));
     tocParagraph.ParagraphProperties = new ParagraphProperties(new Justification() { Val = JustificationValues.Center });
     var tocFieldStart = new Run(new FieldChar() { FieldCharType = FieldCharValues.Begin });
     var tocFieldCode = new Run(new FieldCode("TOC \\o \"1-3\" \\h \\z \\u") { Space = SpaceProcessingModeValues.Preserve });
     var tocFieldSeparator = new Run(new FieldChar() { FieldCharType = FieldCharValues.Separate });
     var tocFieldEnd = new Run(new FieldChar() { FieldCharType = FieldCharValues.End });
     var tocContent = new Paragraph(tocFieldStart, tocFieldCode, tocFieldSeparator, tocFieldEnd);
     body.InsertAt(tocParagraph, 0);
     body.InsertAt(tocContent, 1);
     ForceUpdateFields(body);
 }
 private static void ForceUpdateFields(Body body)
 {
     var mainPart = body.Ancestors<Document>().First().MainDocumentPart;
     var settingsPart = mainPart.DocumentSettingsPart ?? mainPart.AddNewPart<DocumentSettingsPart>();
     if (settingsPart.Settings == null)
         settingsPart.Settings = new DocumentFormat.OpenXml.Wordprocessing.Settings();
     settingsPart.Settings.Append(new UpdateFieldsOnOpen() { Val = true });
 }

Thanks, Renjeesh

for reference cick here