OpenXmlDoc Word: How to add Mark an item for indexing? - openxml

Question

I am using DocumentFormat.OpenXml to generate a Word document programmatically.
In the conceptual content for Word, I can't find any mention for marking items so that they can be included in the document index. What classes can I use for this?
I did a very simple document containing just This is an apple. with an an apple marked for indexing with Main entry: apple. The Xml content is as follows:
<w:p w:rsidR="000975CB" w:rsidRDefault="00B83C06" w:rsidP="007969F3">
<w:r>
<w:t xml:space="preserve">This is </w:t>
</w:r>
<w:r w:rsidR="007969F3"><w:t>an apple</w:t></w:r>
<w:r><w:fldChar w:fldCharType="begin"/></w:r>
<w:r><w:instrText xml:space="preserve"> XE "</w:instrText></w:r>
<w:r w:rsidRPr="00246108"><w:instrText>apple</w:instrText></w:r>
<w:r><w:instrText xml:space="preserve">" </w:instrText></w:r>
<w:r><w:fldChar w:fldCharType="end"/></w:r>
<w:bookmarkStart w:id="0" w:name="_GoBack"/>
<w:bookmarkEnd w:id="0"/>
<w:r><w:t>.</w:t></w:r>
</w:p>
<w:p w:rsidR="007969F3" w:rsidRPr="007969F3" w:rsidRDefault="007969F3" w:rsidP="007969F3"/>
...

Answer 1

An item marked for indexing is a field code (w:instrText) of type XE. A field code has to be inside a complex field character (w:fldChar).
The pertinent markup in the sample document is:
<w:r><w:fldChar w:fldCharType="begin"/></w:r>
<w:r><w:instrText xml:space="preserve"> XE "</w:instrText></w:r>
<w:r><w:instrText>apple</w:instrText></w:r>
<w:r><w:instrText xml:space="preserve">" </w:instrText></w:r>
<w:r><w:fldChar w:fldCharType="end"/></w:r>
The field code elements shown above can be combined together as:
<w:r><w:instrText>XE "apple"</w:instrText></w:r>
Sample code to produce above:
Tuple<Run,Run,Run> MarkEntryForIndex(string item)
{
Run run0 = new Run();
FieldChar fieldChar1 = new FieldChar() { FieldCharType = FieldCharValues.Begin };
run0.Append(fieldChar1);
Run run1 = new Run();
FieldCode fieldCode1 = new FieldCode() { Space = SpaceProcessingModeValues.Preserve };
fieldCode1.Text = " XE \"" + item + "\"";
run1.Append(fieldCode1);
Run run2 = new Run();
FieldChar fieldChar2 = new FieldChar() { FieldCharType = FieldCharValues.End };
run2.Append(fieldChar2);
return Tuple.Create(run0, run1, run2);
}