Get pdf page number by acrofield using itext7 with C#

Question

With iText7, I like to get pdf page number by form field but I can't find method or property of getting page number.

IDictionary<String, PdfFormField> fields = form.GetFormFields();
PdfFormField field = fields["fieldName"];
field.page <-- there is no property

I found this one:

PdfPage page = field.GetWidgets().First().GetPage();

But I have no idea of how to get page number from PdfPage.

It looks like iText5 has this one (in Java):

int page = form.getFieldPositions(name).get(0).page;

And how can I do it with iText 7 in C#

score 6 · Accepted Answer · answered Aug 01 '17 at 11:15

Essentially your problem is

I have no idea of how to get page number from PdfPage.

The class PdfDocument has a method GetPageNumber for this:

/// <summary>Gets page number by page.</summary>
/// <param name="page">the page.</param>
/// <returns>page number.</returns>
public virtual int GetPageNumber(PdfPage page)

Thus, you can retrieve the page number of a page widget like this:

using (PdfReader reader = new PdfReader(formDocumentFile))
using (PdfDocument pdf = new PdfDocument(reader))
{
    PdfAcroForm form = PdfAcroForm.GetAcroForm(pdf, true);
    PdfFormField field = form.GetField(fieldName);
    PdfPage page = field.GetWidgets().First().GetPage();
    int number = pdf.GetPageNumber(page);
    Console.WriteLine("Determined page number: {0}", number);
}

Beware:

field.GetWidgets().First() implicitly assumes that the field has at least one widget. This is not guaranteed, there may be invisible fields without any widgets. In general you should check this.
....GetPage() may return null if the widget annotation is not associated with any page (i.e. neither its own P entry is set nor is it referenced from any current page). In general you should check this.

Get pdf page number by acrofield using itext7 with C#

1 Answers1