FieldBuilder

public FieldBuilder(FieldType fieldType)

Document doc = new Document();

// A convenient way of adding text content to a document is with a document builder.
DocumentBuilder builder = new DocumentBuilder(doc);
builder.Write(" Hello world! This text is one Run, which is an inline node.");

// Fields have their builder, which we can use to construct a field code piece by piece.
// In this case, we will construct a BARCODE field representing a US postal code,
// and then insert it in front of a Run.
FieldBuilder fieldBuilder = new FieldBuilder(FieldType.FieldBarcode);
fieldBuilder.AddArgument("90210");
fieldBuilder.AddSwitch("\\f", "A");
fieldBuilder.AddSwitch("\\u");

fieldBuilder.BuildAndInsert(doc.FirstSection.Body.FirstParagraph.Runs[0]);

doc.UpdateFields();
doc.Save(ArtifactsDir + "Field.CreateWithFieldBuilder.docx");