Get the export value of a checkbox using iTextSharp

Question

I\'m working on dynamically filling in the fields on a pdf document using ITextSharp. I\'d like to be able to determine the \"export value\" of the checkbox is from the cod

Answer 1

I couldn't get the answer Mark to work for me because the appearanceDict was always null. Here is a method I wrote that works for the CheckBox and RadioButton controls on the forms I'm dealing with.

private static string GetAnswerValue(AcroFields.Item f, int i)
{
    var widg = f.GetWidget(i);
    if (widg == null)
        return null;
    var ap = widg.GetAsDict(PdfName.AP);
    if (ap == null)
        return null;

    //PdfName.D also seems to work
    var d = ap.GetAsDict(PdfName.N);
    if (d == null)
        return null;
    var e = d.Keys.FirstOrDefault(n => !n.Equals(PdfName.OFF));
    if (e == null)
        return null;
    return e.ToString().Substring(1);
}

Answer 2

Okay, you need to check the low-level PDF objects for the appropriate values. You can look up said values in the PDF Reference (chapter 12: Interactive Features, section 7: Interactive Forms).

In particular (and in Java):

AcroFields.Item item = acroFields.getFieldItem(fldName);
PdfDictionary valueDict = item.getValue(0);

PdfDictionary appearanceDict = valueDict .getAsDict(PdfName.AP);

if (appearanceDict != null) {
  PdfDictionary normalAppearances = appearanceDict.getAsDict(PdfName.N);
  // /D is for the "down" appearances.

  // if there are normal appearances, one key will be "Off", and the other
  // will be the export value... there should only be two.
  if (normalAppearances != null) {
    Set<PdfName> keys = normalAppearances .getKeys();
    for (PdfName curKey : keys) {
      if (!PdfName.OFF.equals(curKey)) {
        return curKey.toString(); // string will have a leading '/' character
      }
    }
  }


}
// if that doesn't work, there might be an /AS key, whose value is a name with 
// the export value, again with a leading '/'
PdfName curVal = valueDict.getAsName(PdfName.AS);
if (curVal != null) {
  return curVal.toString();
}

Something like that. The usual "I just wrote this in the edit box here" provisions apply, but that should be good to go. I write a distressingly large amount of low level iText code.

Answer 3

The best way I found to set a checkbox is:

    void SetCB(AcroFields fields, string F)
    {
        try
        {
            fields.SetField(F, fields.GetFieldItem(F).GetValue(0).GetAsDict(PdfName.AP).GetAsDict(PdfName.N).Keys.Single().ToString().TrimStart('/'));
        } catch { }
    }

error: Sequence contains more than one element

e.g:

       PdfReader reader = new PdfReader("c:\\qqq\\fl100Y2.pdf");// formFile);
        using (PdfStamper stamper = new PdfStamper(reader, new FileStream("c:\\qqq\\fl100Ynew.pdf", FileMode.Create)))
        {
            AcroFields fields = stamper.AcroFields;

            bool set = fields.SetFieldProperty("FillText156", "textsize", 10.0f, null);
            SetCB(fields, "CheckBox24");
            SetCB(fields, "CheckBox24by");
             fields.SetField("FillText156", "John Doe");
            // flatten form fields and close document
            stamper.FormFlattening = true;
            stamper.Close();
        }

Answer 4

This was the final method I used to get it working based on the others:

    public string GetCheckBoxExportValue(AcroFields fields, string cbFieldName)
    {
        AcroFields.Item item = fields.GetFieldItem(cbFieldName);
        if (item.values.Count > 0)
        {
            PdfDictionary valueDict = item.values[0] as PdfDictionary;
            PdfDictionary appDict = valueDict.GetAsDict(PdfName.AP);

            if (appDict != null)
            {
                PdfDictionary normalApp = appDict.GetAsDict(PdfName.N);

                foreach (PdfName curKey in normalApp.Keys)
                {
                    if (!PdfName.OFF.Equals(curKey))
                    {
                        // string will have a leading '/' character
                        return curKey.ToString(); 
                    }
                }
            }

            PdfName curVal = valueDict.GetAsName(PdfName.AS);
            if (curVal != null)
            {
                return curVal.ToString();
            }

        }

        return null;
    }