Check Word Doc for Field Code before applying - vb.net

Question

So I've coded a VSTO addin using vb.net to add a header to a document in Word however from historical methods we have lots of templates with field codes. My addin does not account for these and simply strips the header to add xxxxx value you choose from the pop up.
I need my code to be smart enough to 'spot' the field code and append or if it does not exist e.g. a blank document then continue running as expected. I can append this field code using the below code:
wordDocument.Variables("fieldname").Value = "xxxx"
wordDocument.Fields.Update
However my tool then adds the header as normal and strips most the content from the template. So effectively my question is how would I code a check for this before proceeding. So in plain English I would need my addin to go from this:
Load pop up
Set xxxx value in header
Close
To this:
Load pop up
Check Document for existing "fieldname"
If "fieldname" exists then
wordDocument.Variables("fieldname").Value = "xxxx" (from pop up selection)
wordDocument.Fields.Update
However if "fieldname" doesn't exist then continue as normal....
Sorry if this is a little complex and/or long winded.
Thanks in advance.

Answer 1

Here is my code in C#, hope this might help you to code in VB.Net
foreach (Section sec in doc.Sections)
{
doc.ActiveWindow.View.set_SeekView(WdSeekView.wdSeekCurrentPageHeader);
foreach (HeaderFooter headerFooter in sec.GetHeadersFooters())
{
doc.ActiveWindow.View.set_SeekView(headerFooter.IsHeader ? WdSeekView.wdSeekCurrentPageHeader : WdSeekView.wdSeekCurrentPageFooter);
if (headerFooter.Range.Fields.Count > 0)
{
//Append to existing fields
UpdateFields(headerFooter.Range.Fields);
}
else
{
//Add field code
AddFieldCode(headerFooter.Range);
}
}
doc.ActiveWindow.View.set_SeekView(WdSeekView.wdSeekMainDocument);
}
Extension method to iterate through the header types
public static IEnumerable<HeaderFooter> GetHeadersFooters(this Section section)
{
List<HeaderFooter> headerFooterlist = new List<HeaderFooter>
{
section.Headers[WdHeaderFooterIndex.wdHeaderFooterPrimary],
section.Headers[WdHeaderFooterIndex.wdHeaderFooterFirstPage],
section.Headers[WdHeaderFooterIndex.wdHeaderFooterEvenPages],
section.Footers[WdHeaderFooterIndex.wdHeaderFooterPrimary],
section.Footers[WdHeaderFooterIndex.wdHeaderFooterFirstPage],
section.Footers[WdHeaderFooterIndex.wdHeaderFooterEvenPages]
};
return headerFooterlist;
}