c# - underline portion of text using iTextSharp

Question

I have an application that uses itextsharp to fill PDF form fields.

One of these fields has some text with tags. For example:

<U>This text should be underlined</>. 

I'd like that the text closed in .. has to be underlined.

How could I do that?

How could I approch it with HTMLWorker for example?

Here's the portion of code where I write my description:

for (int i = 0; i < linesDescription.Count; i++)
{
         int count = linesDescription[i].Count();
         int countTrim = linesDescription[i].Trim().Count();
         Chunk cnk = new Chunk(linesDescription[i] + GeneralPurpose.ReturnChar, TextStyle);

         if (firstOpe && i > MaxLinePerPage - 1)
               LongDescWrapped_dt_extra.Add(cnk);
         else
               LongDescWrapped_dt.Add(cnk);
}

Answer 1

Ordinary text fields do not support rich text. If you want the fields to remain interactive, you will need RichText fields. These are fields that are flagged in a way that they accept an RV value. This is explained here: Set different parts of a form field to have different fonts using iTextSharp (Note that I didn't succeed in getting this to work, but you may have better luck.)

If it is OK for you to flatten the form (i.e. remove all interactivity), please take a look at the FillWithUnderline example:

public void manipulatePdf(String src, String dest) throws DocumentException, IOException {
    PdfReader reader = new PdfReader(src);
    PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(dest));
    stamper.setFormFlattening(true);
    AcroFields form = stamper.getAcroFields();
    FieldPosition pos = form.getFieldPositions("Name").get(0);
    ColumnText ct = new ColumnText(stamper.getOverContent(pos.page));
    ct.setSimpleColumn(pos.position);
    ElementList elements = XMLWorkerHelper.parseToElementList("<div>Bruno <u>Lowagie</u></div>", null);
    for (Element element : elements) {
        ct.addElement(element);
    }
    ct.go();
    stamper.close();
}

In this example, we don't fill out the field, but we get the fields position (a page number and a rectangle). We then use ColumnText to add content at this position. As we are inputting HTML, we use XML Worker to parse the HTML into iText objects that we can add to the ColumnText object.

This is a Java example, but it should be easy to port this to C# if you know how to code in C# (which I don't).