Populate PdfRadioButtonField using PDFSharp

Question

I'm using PDFSharp version 1.50.4740-beta5 from http://www.pdfsharp.net which I installed from NuGet.

I'm able to fill text form fields and checkbox form fields but I can't get radio buttons to work at all. I don't get an error. SelectedIndex is -1 before and after I set it to 1.

Several at articles on Stack Overflow have helped me to get this far. Has anyone successfully populated radio button form fields using this product? Here is a link to the sample PDF: http://www.myblackmer.com/bluebook/interactiveform_enabled.pdf

(Before you suggest iTextPdf, I've already evaluated it and Aspose.PDF and they are not practical)

        //using PdfSharp.Pdf.IO;
        //using PdfSharp.Pdf;
        //using PdfSharp.Pdf.AcroForms;
        string fileName = "x:\\interactiveform_enabled.pdf";
        PdfSharp.Pdf.PdfDocument pdfDocument = PdfReader.Open(fileName);

        //The populated fields are not visible by default
        if (pdfDocument.AcroForm.Elements.ContainsKey("/NeedAppearances"))
        {
            pdfDocument.AcroForm.Elements["/NeedAppearances"] = new PdfBoolean(true);
        }
        else
        {
            pdfDocument.AcroForm.Elements.Add("/NeedAppearances", new PdfBoolean(true));
        }

        PdfRadioButtonField currentField = (PdfRadioButtonField)(pdfDocument.AcroForm.Fields["Sex"]);
        currentField.ReadOnly = false;
        currentField.SelectedIndex = 1;

        pdfDocument.Flatten();
        pdfDocument.Save("x:\\interactiveform_enabled_2.pdf");

Answer 1

Since this is #1 in a Google search for "PDFSharp radio buttons", figured I'd share what seems to be working for me.

I created extension functions for the PdfRadioButtonField object that:

• Gets all option values and their indexes
• Sets the value for a radio field by index number
• Sets the value for a radio field by value

In the following examples, ErPdfRadioOption is:

public class ErPdfRadioOption
{
    public int Index { get; set; }
    public string Value { get; set; }
}

Get all available options for a radio field

public static List<ErPdfRadioOption> FindOptions(this PdfRadioButtonField source) {
    if (source == null) return null;
    List<ErPdfRadioOption> options = new List<ErPdfRadioOption>();

    PdfArray kids = source.Elements.GetArray("/Kids");

    int i = 0;
    foreach (var kid in kids) {
        PdfReference kidRef = (PdfReference)kid;
        PdfDictionary dict = (PdfDictionary)kidRef.Value;
        PdfDictionary dict2 = dict.Elements.GetDictionary("/AP");
        PdfDictionary dict3 = dict2.Elements.GetDictionary("/N");

        if (dict3.Elements.Keys.Count != 2)
            throw new Exception("Option dictionary should only have two values");

        foreach (var key in dict3.Elements.Keys)
            if (key != "/Off") { // "Off" is a reserved value that all non-selected radio options have
                ErPdfRadioOption option = new ErPdfRadioOption() { Index = i, Value = key };
                options.Add(option);
            }
        i++;
    }

    return options;
}

Usage

PdfDocument source;
PdfAcroField field = source.AcroForm.Fields[...]; //name or index of the field
PdfRadioButtonField radioField = field as PdfRadioButtonField;
return radioField.FindOptions();

Result (JSON)

[
  {
    "Index": 0,
    "Value": "/Choice1"
  },
  {
    "Index": 1,
    "Value": "/Choice2"
  },
  {
    "Index": 2,
    "Value": "/Choice3"
  }
]

Set the option for a radio field by index

You'd think this is what the SelectedIndex property should be for... but apparently not.

public static void SetOptionByIndex(this PdfRadioButtonField source,int index) {
    if (source == null) return;
    List<ErPdfRadioOption> options = source.FindOptions();
    ErPdfRadioOption selectedOption = options.Find(x => x.Index == index);
    if (selectedOption == null) return; //The specified index does not exist as an option for this radio field
    
    // https://forum.pdfsharp.net/viewtopic.php?f=2&t=3561
    PdfArray kids = (PdfArray)source.Elements["/Kids"];
    int j = 0;
    foreach (var kid in kids) {
        var kidValues = ((PdfReference)kid).Value as PdfDictionary;
        //PdfRectangle rectangle = kidValues.Elements.GetRectangle(PdfAnnotation.Keys.Rect);
        if (j == selectedOption.Index)
            kidValues.Elements.SetValue("/AS", new PdfName(selectedOption.Value));
        else
            kidValues.Elements.SetValue("/AS", new PdfName("/Off"));
        j++;
    }
}

Note: This depends on the FindOptions() function above.

Usage

PdfDocument source;
PdfAcroField field = source.AcroForm.Fields[...]; //name or index of the field
PdfRadioButtonField radioField = field as PdfRadioButtonField;
radioField.SetOptionByIndex(index);

Set the option for a radio field by value

public static void SetOptionByValue(this PdfRadioButtonField source, string value) {
    if (source == null || string.IsNullOrWhiteSpace(value)) return;
    if (!value.StartsWith("/", StringComparison.OrdinalIgnoreCase)) value = "/" + value; //All values start with a '/' character
    List<ErPdfRadioOption> options = source.FindOptions();
    ErPdfRadioOption selectedOption = options.Find(x => x.Value == value);
    if (selectedOption == null) return; //The specified index does not exist as an option for this radio field
    source.SetOptionByIndex(selectedOption.Index);
}

Note: This depends on the FindOptions() and SetOptionByIndex() functions above.

Based on this post in the PDFsharp forum: https://forum.pdfsharp.net/viewtopic.php?f=2&t=3561#p11386

Using PDFsharp version 1.50.5147