//// This code is part of Document Solutions for PDF .NET demos.// Copyright (c) MESCIUS inc. All rights reserved.//using System;using System.IO;using GrapeCity.Documents.Pdf;using GrapeCity.Documents.Pdf.AcroForms;using GrapeCity.Documents.Pdf.Spec;using DsPdfWeb.Demos.Common;
namespace DsPdfWeb.Demos{    // This example shows how to load a password protected PDF Form without specifying the password,    // and change the value of a text field and a comb-text field in the form.    // The modified PDF is saved and re-opened with the password so that we can show it in the demo.    public class NoPassSetFormFields    {        public int CreatePDF(Stream stream)        {            using var fsSrc = File.OpenRead(Path.Combine("Resources", "PDFs", "FormFields-password-user.pdf"));            // Set up DecryptionOptions to allow loading password protected PDFs without password:            var dopt = new DecryptionOptions() { ThrowExceptionIfInvalidPassword = false };            var docSrc = new GcPdfDocument();            docSrc.Load(fsSrc, dopt);
            // Change the value of CheckBoxField            //            // Note 1:            // We cannot access the fields by names, like:            //   doc.AcroForm.Fields["cbf1"];            // because strings in a password protected PDF are encrypted            // and cannot be accessed without specifying the password.            // The only way is to access fields by indices.            var cbf = (CheckBoxField)docSrc.AcroForm.Fields[0];            cbf.Checked = true;
            // Change the value of RadioButtonField:            var rbf = (RadioButtonField)docSrc.AcroForm.Fields[1];            var values = rbf.GetCheckedAppearanceStreamNames();            rbf.Value = values[0];
            // Change the value of the TextField, set it to the current date/time:            var tf = (TextField)docSrc.AcroForm.Fields[2];            // Note 2:            // The value of a TextField is specified as a string, but it is not possible            // to work with strings in a password protected PDF without specifying the password.            // In such cases it is possible to use a workaround to set it using PdfName,            // while it is not compliant with the PDF specification,            // at least Adobe Acrobat supports this scenario:            tf.PdfValue = new PdfName(Common.Util.TimeNow().ToString());
            // Change the value of a CombTextField to a random string:            var ctf = (CombTextField)docSrc.AcroForm.Fields[3];            var val = Util.LoremIpsum(1, 1, 1, 2, 3);            val = val.Substring(0, Math.Min(val.Length, 10));            ctf.PdfValue = new PdfName(val);
            // Note 3: appearance streams cannot be generated in a password protected PDF            // that was loaded without specifying the password, so we set            // the NeedAppearances entry of the AcroForm, which instructs Acrobat to generate            // the missing appearance streams:            docSrc.AcroForm.Set(PdfName.Std.NeedAppearances, PdfBool.True);
            // Demo site specific:            // We save the modified password protected document to a temp file,            // and load it again with the password, so that the demo site can show it            // without asking the user for a password (the block is to delete the temp file):            var fn = Path.GetTempFileName();            {                docSrc.Save(fn);                var doc = new GcPdfDocument();                using var fs = File.OpenRead(fn);                doc.Load(fs, "user");                doc.Save(stream);            }            File.Delete(fn);            return docSrc.Pages.Count;        }    }}