Create PDF Forms from Code

The fields of an interactive PDF form can be created from code in a document being created with PdfDocument or added to an existing document loaded in PdfEditor, with the PdfDocumentAddFormField(PdfFormField) and PdfEditorAddFormField(PdfFormField) methods. The fields have a name, a position, a size and an appearance, they can be required or read-only and they can carry scripts and actions executed by the PDF viewer. The fields of a HTML form are converted automatically by the HTML to PDF converter, as described in the Auto Create PDF Forms from HTML Forms topic; this topic describes the fields created from code.

The demo application creates a registration form with text fields, a comb field, a combo box, radio buttons, a multiple selection list box, check boxes, a multiline text field, a read-only calculated field and push buttons with submit, reset, print, hide, go to page and open URL actions, together with a document level script that defines a function used by the validate script of the email field. The fields can be flattened to static content and the document can be generated as PDF/A, in which case the actions and the scripts are left out, because the standard does not allow them.

Field Types

All the fields derive from PdfFormField, which gives them the Name, Description, Required, ReadOnly and Exportable properties. The fields displayed in one rectangle of a page derive from PdfWidgetFormField, which adds the page number, the position, the size, the colors and the border style. PdfTextField is a text box, single line, multiline, password, comb with a fixed number of cells or limited to a maximum length. PdfCheckBoxField is a check box with a check mark style and an export value. PdfComboBoxField and PdfListBoxField derive from PdfChoiceFormField and display options added with PdfChoiceFormFieldAddOption(String, String); the list box can allow several selections. PdfRadioGroupField is a group of radio buttons with one selected value, each button being added to a page with PdfRadioGroupFieldAddButton(String, Int32, Single, Single, Single, Single). PdfPushButtonField is a button with a caption, an optional icon and an action.

Create Fields of Several Types
// A text field with a maximum length displayed in separate cells
PdfTextField accessCodeField = new PdfTextField("accessCode", 1, 130, 110, 120, 22)
{
    Font = fieldFont,
    BorderColor = PdfColor.Gray,
    MaxLength = 6,
    Comb = true,
    Description = "Six character access code"
};
pdfDocument.AddFormField(accessCodeField);

// A combo box with a selected option
PdfComboBoxField countryField = new PdfComboBoxField("country", 1, 130, 144, 180, 22) { Font = fieldFont };
countryField.AddOption("Austria", "AT");
countryField.AddOption("Romania", "RO");
countryField.SelectedValue = "RO";
pdfDocument.AddFormField(countryField);

// A group of radio buttons; each button is placed in a page
PdfRadioGroupField ticketField = new PdfRadioGroupField("ticketType") { SelectedValue = "standard" };
ticketField.AddButton("standard", 1, 130, 181, 14, 14);
ticketField.AddButton("premium", 1, 230, 181, 14, 14);
pdfDocument.AddFormField(ticketField);

Field Positions and Appearance

In a document being created the X and Y positions are given in points from the top left corner of the content area of the page, inside the margins, like the positions of the text and image elements. In an edited document they are given from the top left corner of the page. The text of a field is written with its Font; a standard font can be used in a plain document, while a PDF/A or PDF/UA document needs an embedded font, created with {{M:PdfFontManager.CreateBaseFont(System.String,System.Boolean,System.Collections.Generic.IList{System.Int32[]})}} with the subset parameter set to false, so that the viewer can display any value typed in the field.

The border of a field is drawn with its BorderColor, BorderWidth and BorderStyle, one of the PdfFormFieldBorderStyle values, over the BackgroundColor. The check mark of a check box or radio button is one of the PdfCheckBoxStyle values set in Style or Style, drawn with the SymbolColor. Visibility hides a field on screen, in print or both.

Scripts and Actions

The Actions property gives the events of a field: Keystroke, Format, Validate and Calculate take a PdfJavaScriptAction with the script run by the viewer and the mouse and focus events take any PdfFieldAction. A push button runs its Action: PdfSubmitFormAction sends the field values to a web address in the PdfSubmitFormat of its Format property, PdfResetFormAction clears the fields, PdfNamedAction runs a viewer command such as printing, PdfHideFieldsAction shows or hides fields, PdfGoToPageAction goes to a page, PdfGoToNamedDestinationAction goes to a named destination and PdfOpenUrlAction opens a web address. A document level script, which can define functions used by the scripts of the fields, is added with PdfDocumentAddJavaScript(String).

Add Scripts and Actions
// The total is computed by the viewer from the other fields
totalField.Actions.Calculate = new PdfJavaScriptAction(
    "var prices = { standard: 350, premium: 500, student: 120 };" +
    "event.value = prices[this.getField('ticketType').value] || 0;");

// The buttons submit the form as FDF, reset it and print the document
submitButton.Action = new PdfSubmitFormAction("https://www.example.com/register") { Format = PdfSubmitFormat.Fdf };
resetButton.Action = new PdfResetFormAction(null);
printButton.Action = new PdfNamedAction(PdfNamedActionType.Print);

// The document level script defines a function used by the validate script of the email field
pdfDocument.AddJavaScript("function isValidEmail(value) { return value.length == 0 || value.indexOf('@') > 0; }");
emailField.Actions.Validate = new PdfJavaScriptAction(
    "if (!isValidEmail(event.value)) { app.alert('The email address is not valid'); event.rc = false; }");

Flatten the Fields

When Flatten is true the fields are drawn as static page content when the document is saved, with their current values and the document has no interactive form. The same flag exists in PdfEditor as Flatten. The fields of a loaded document can also be flattened one by one, as described in the Fill, Flatten and Edit PDF Forms topic.

Code Sample - Create PDF Forms from Code

C#
using System.IO;
using System.ComponentModel.DataAnnotations;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Mvc;
using EvoPdf_Next_AspNetDemo.Models;
using EvoPdf_Next_AspNetDemo.Models.PDF_Creator;

// Use EVO PDF Namespace
using EvoPdf.Next;

namespace EvoPdf_Next_AspNetDemo.Controllers.PDF_Creator
{
    public class Create_PDF_Forms_from_CodeController : Controller
    {
        private readonly IWebHostEnvironment m_hostingEnvironment;

        public Create_PDF_Forms_from_CodeController(IWebHostEnvironment hostingEnvironment)
        {
            m_hostingEnvironment = hostingEnvironment;
        }

        public IActionResult Index()
        {
            var model = new Create_PDF_Forms_from_Code_ViewModel();
            return View(model);
        }

        [HttpPost]
        public ActionResult CreatePdf(Create_PDF_Forms_from_Code_ViewModel model)
        {
            if (!ModelState.IsValid)
            {
                var errorMessage = ModelStateHelper.GetModelErrors(ModelState);
                throw new ValidationException(errorMessage);
            }

            // Set the license key received after purchase to use the library in licensed mode; leave it commented for demo mode
            // Licensing.LicenseKey = "your-license-key";

            PdfDocumentCreateSettings pdfCreateSettings = new PdfDocumentCreateSettings()
            {
                PageSize = PdfPageSize.A4,
                PageOrientation = PdfPageOrientation.Portrait,
                Margins = new PdfMargins(40, 40, 40, 40),
                PdfStandard = model.PdfStandard,
                Language = "en-US"
            };

            using PdfDocument pdfDocument = new PdfDocument(pdfCreateSettings);
            pdfDocument.PdfDocumentInfo.Title = "Conference Registration";

            // The fields are drawn as static content instead of interactive fields
            pdfDocument.Flatten = model.FlattenFields;

            // PDF/A documents have no actions and no scripts
            bool pdfA = PdfStandardIsPdfA(model.PdfStandard);
            bool addActions = model.AddFieldActions && !pdfA;

            string fontsPath = GetDemoFontsPath();
            PdfBaseFont baseFont = PdfFontManager.CreateBaseFont(Path.Combine(fontsPath, "DejaVuSerif.ttf"));
            PdfFont titleFont = PdfFontManager.CreateFont(baseFont, 18f, PdfFontStyle.Bold, PdfColor.DarkBlue);
            PdfFont labelFont = PdfFontManager.CreateFont(baseFont, 11f, PdfFontStyle.Normal, PdfColor.Black);
            PdfFont noteFont = PdfFontManager.CreateFont(baseFont, 9f, PdfFontStyle.Normal, PdfColor.DarkGray);

            // The text of the fields is written with a standard font in a document without a standard and with
            // the embedded font in a PDF/A or PDF/UA document
            PdfFont fieldFont = model.PdfStandard == PdfStandard.None
                ? PdfFontManager.CreateStandardFont(PdfStandardFont.Helvetica, 10f, PdfColor.Black)
                : PdfFontManager.CreateFont(PdfFontManager.CreateBaseFont(Path.Combine(fontsPath, "DejaVuSerif.ttf"), false), 10f, PdfColor.Black);

            PdfColor borderColor = PdfColor.Gray;
            const float fieldLeft = 130;
            const float fieldWidth = 260;
            float crtYPos = 0;

            pdfDocument.AddText(new PdfTextElement("Conference Registration", titleFont) { X = 0, Y = crtYPos });
            crtYPos += 40;

            // The field positions are relative to the content area of the page, like the positions of the text elements
            AddLabel(pdfDocument, "Full name", labelFont, crtYPos);
            PdfTextField fullNameField = new PdfTextField("fullName", 1, fieldLeft, crtYPos, fieldWidth, 22)
            {
                Font = fieldFont,
                BorderColor = borderColor,
                BorderStyle = model.BorderStyle,
                BackgroundColor = PdfColor.FromHex("#F4F6F8"),
                Description = "Full name",
                Required = model.RequiredFields,
                Text = "Jane Doe"
            };
            if (addActions)
            {
                // The name is shown in capitals while it is typed and when the field loses the focus
                fullNameField.Actions.Keystroke = new PdfJavaScriptAction("event.change = event.change.toUpperCase();");
                fullNameField.Actions.Format = new PdfJavaScriptAction("event.value = event.value.toUpperCase();");
            }
            pdfDocument.AddFormField(fullNameField);
            crtYPos += 34;

            AddLabel(pdfDocument, "Email", labelFont, crtYPos);
            PdfTextField emailField = new PdfTextField("email", 1, fieldLeft, crtYPos, fieldWidth, 22)
            {
                Font = fieldFont,
                BorderColor = borderColor,
                BorderStyle = model.BorderStyle,
                Description = "Email address",
                Required = model.RequiredFields
            };
            if (addActions)
            {
                // The address is validated when the field is committed. The validation uses the function
                // defined by the document level script when the script is added to the document
                string validateScript = model.AddDocumentScript
                    ? "if (!isValidEmail(event.value)) { app.alert('The email address is not valid'); event.rc = false; }"
                    : "if (event.value.length > 0 && event.value.indexOf('@') < 0) { app.alert('The email address is not valid'); event.rc = false; }";
                emailField.Actions.Validate = new PdfJavaScriptAction(validateScript);
            }
            pdfDocument.AddFormField(emailField);
            crtYPos += 34;

            AddLabel(pdfDocument, "Access code", labelFont, crtYPos);
            pdfDocument.AddFormField(new PdfTextField("accessCode", 1, fieldLeft, crtYPos, 120, 22)
            {
                Font = fieldFont,
                BorderColor = borderColor,
                BorderStyle = model.BorderStyle,
                MaxLength = 6,
                Comb = true,
                Description = "Six character access code"
            });
            crtYPos += 34;

            AddLabel(pdfDocument, "Country", labelFont, crtYPos);
            PdfComboBoxField countryField = new PdfComboBoxField("country", 1, fieldLeft, crtYPos, 180, 22)
            {
                Font = fieldFont,
                BorderColor = borderColor,
                BorderStyle = model.BorderStyle,
                Description = "Country"
            };
            countryField.AddOption("Austria", "AT");
            countryField.AddOption("France", "FR");
            countryField.AddOption("Germany", "DE");
            countryField.AddOption("Italy", "IT");
            countryField.AddOption("Spain", "ES");
            countryField.SelectedValue = "DE";
            pdfDocument.AddFormField(countryField);
            crtYPos += 34;

            AddLabel(pdfDocument, "Ticket type", labelFont, crtYPos);
            PdfRadioGroupField ticketField = new PdfRadioGroupField("ticketType")
            {
                SelectedValue = "standard",
                SymbolColor = PdfColor.DarkBlue,
                Description = "Ticket type"
            };
            string[] ticketValues = { "standard", "premium", "student" };
            string[] ticketCaptions = { "Standard", "Premium", "Student" };
            for (int i = 0; i < ticketValues.Length; i++)
            {
                PdfRadioButton button = ticketField.AddButton(ticketValues[i], 1, fieldLeft + i * 100, crtYPos + 3, 14, 14);
                button.BorderColor = borderColor;
                button.BorderStyle = model.BorderStyle;
                pdfDocument.AddText(new PdfTextElement(ticketCaptions[i], labelFont) { X = fieldLeft + 20 + i * 100, Y = crtYPos + 3 });
            }
            pdfDocument.AddFormField(ticketField);
            crtYPos += 34;

            AddLabel(pdfDocument, "Sessions", labelFont, crtYPos);
            PdfListBoxField sessionsField = new PdfListBoxField("sessions", 1, fieldLeft, crtYPos, fieldWidth, 70)
            {
                Font = fieldFont,
                BorderColor = borderColor,
                BorderStyle = model.BorderStyle,
                MultiSelect = true,
                Description = "Sessions to attend"
            };
            sessionsField.AddOption("Keynote");
            sessionsField.AddOption("Workshop: PDF generation");
            sessionsField.AddOption("Workshop: Accessibility");
            sessionsField.AddOption("Panel discussion");
            sessionsField.AddOption("Networking dinner");
            sessionsField.SelectedValues.Add("Keynote");
            pdfDocument.AddFormField(sessionsField);
            crtYPos += 82;

            AddLabel(pdfDocument, "Options", labelFont, crtYPos);
            pdfDocument.AddFormField(new PdfCheckBoxField("newsletter", 1, fieldLeft, crtYPos + 3, 14, 14)
            {
                BorderColor = borderColor,
                BorderStyle = model.BorderStyle,
                Style = model.CheckBoxStyle,
                Checked = true,
                Description = "Receive the newsletter"
            });
            pdfDocument.AddText(new PdfTextElement("Receive the newsletter", labelFont) { X = fieldLeft + 20, Y = crtYPos + 3 });
            pdfDocument.AddFormField(new PdfCheckBoxField("terms", 1, fieldLeft, crtYPos + 25, 14, 14)
            {
                BorderColor = borderColor,
                BorderStyle = model.BorderStyle,
                Style = model.CheckBoxStyle,
                Required = model.RequiredFields,
                Description = "Accept the terms"
            });
            pdfDocument.AddText(new PdfTextElement("I accept the terms and conditions", labelFont) { X = fieldLeft + 20, Y = crtYPos + 25 });
            crtYPos += 56;

            AddLabel(pdfDocument, "Comments", labelFont, crtYPos);
            pdfDocument.AddFormField(new PdfTextField("comments", 1, fieldLeft, crtYPos, fieldWidth, 70)
            {
                Font = fieldFont,
                BorderColor = borderColor,
                BorderStyle = model.BorderStyle,
                Multiline = true,
                DoNotSpellCheck = true,
                Description = "Comments"
            });
            crtYPos += 82;

            AddLabel(pdfDocument, "Total (EUR)", labelFont, crtYPos);
            PdfTextField totalField = new PdfTextField("total", 1, fieldLeft, crtYPos, 100, 22)
            {
                Font = fieldFont,
                BorderColor = borderColor,
                BorderStyle = model.BorderStyle,
                ReadOnly = true,
                Alignment = PdfTextAlignment.Right,
                Text = "350",
                Description = "Total amount"
            };
            if (addActions)
            {
                // The total follows the ticket type and the number of sessions
                totalField.Actions.Calculate = new PdfJavaScriptAction(
                    "var prices = { standard: 350, premium: 500, student: 120 };" +
                    "var ticket = this.getField('ticketType').value;" +
                    "var sessions = this.getField('sessions').value;" +
                    "var count = sessions == null ? 0 : (typeof sessions == 'string' ? 1 : sessions.length);" +
                    "event.value = (prices[ticket] || 0) + count * 25;");
            }
            pdfDocument.AddFormField(totalField);
            crtYPos += 40;

            // The buttons: submit, reset, print and the navigation to the second page
            PdfPushButtonField submitButton = new PdfPushButtonField("submit", 1, fieldLeft, crtYPos, 100, 26, "Submit")
            {
                Font = fieldFont,
                BackgroundColor = PdfColor.LightGray,
                BorderColor = borderColor,
                BorderStyle = model.BorderStyle,
                Description = "Submit the form"
            };
            PdfPushButtonField resetButton = new PdfPushButtonField("reset", 1, fieldLeft + 110, crtYPos, 100, 26, "Reset")
            {
                Font = fieldFont,
                BackgroundColor = PdfColor.LightGray,
                BorderColor = borderColor,
                BorderStyle = model.BorderStyle,
                Description = "Reset the form"
            };
            PdfPushButtonField printButton = new PdfPushButtonField("print", 1, fieldLeft + 220, crtYPos, 100, 26, "Print")
            {
                Font = fieldFont,
                BackgroundColor = PdfColor.LightGray,
                BorderColor = borderColor,
                BorderStyle = model.BorderStyle,
                Description = "Print the form"
            };
            if (addActions)
            {
                // The form data is sent as FDF to the given address; the reset action clears all the fields
                // and the named action opens the print dialog of the viewer
                submitButton.Action = new PdfSubmitFormAction("https://www.example.com/register") { Format = PdfSubmitFormat.Fdf };
                resetButton.Action = new PdfResetFormAction(null);
                printButton.Action = new PdfNamedAction(PdfNamedActionType.Print);
            }
            pdfDocument.AddFormField(submitButton);
            pdfDocument.AddFormField(resetButton);
            pdfDocument.AddFormField(printButton);
            crtYPos += 40;

            PdfPushButtonField hideButton = new PdfPushButtonField("hideComments", 1, fieldLeft, crtYPos, 100, 26, "Hide comments")
            {
                Font = fieldFont,
                BackgroundColor = PdfColor.LightGray,
                BorderColor = borderColor,
                BorderStyle = model.BorderStyle,
                Exportable = false
            };
            PdfPushButtonField nextPageButton = new PdfPushButtonField("nextPage", 1, fieldLeft + 110, crtYPos, 100, 26, "Next page")
            {
                Font = fieldFont,
                BackgroundColor = PdfColor.LightGray,
                BorderColor = borderColor,
                BorderStyle = model.BorderStyle,
                Exportable = false
            };
            PdfPushButtonField siteButton = new PdfPushButtonField("website", 1, fieldLeft + 220, crtYPos, 100, 26, "Web site")
            {
                Font = fieldFont,
                BackgroundColor = PdfColor.LightGray,
                BorderColor = borderColor,
                BorderStyle = model.BorderStyle,
                Exportable = false
            };
            if (addActions)
            {
                hideButton.Action = new PdfHideFieldsAction(new[] { "comments" }, true);
                nextPageButton.Action = new PdfGoToPageAction(2, PdfLinkPageLocation.FitPage());
                siteButton.Action = new PdfOpenUrlAction("https://www.example.com");
            }
            pdfDocument.AddFormField(hideButton);
            pdfDocument.AddFormField(nextPageButton);
            pdfDocument.AddFormField(siteButton);
            crtYPos += 44;

            pdfDocument.AddText(new PdfTextElement("The fields marked as required must be filled before the form is submitted", noteFont) { X = 0, Y = crtYPos });

            // The second page holds a field of the same radio group and a hidden field
            pdfDocument.AddPage();
            pdfDocument.AddText(new PdfTextElement("Accommodation", titleFont) { X = 0, Y = 0 });
            AddLabel(pdfDocument, "Hotel room", labelFont, 40);
            PdfRadioGroupField roomField = new PdfRadioGroupField("hotelRoom")
            {
                SymbolColor = PdfColor.DarkBlue,
                AllowDeselect = true,
                Description = "Hotel room"
            };
            roomField.AddButton("single", 2, fieldLeft, 43, 14, 14).BorderColor = borderColor;
            pdfDocument.AddText(new PdfTextElement("Single", labelFont) { X = fieldLeft + 20, Y = 43 });
            roomField.AddButton("double", 2, fieldLeft + 100, 43, 14, 14).BorderColor = borderColor;
            pdfDocument.AddText(new PdfTextElement("Double", labelFont) { X = fieldLeft + 120, Y = 43 });
            pdfDocument.AddFormField(roomField);

            AddLabel(pdfDocument, "Arrival date", labelFont, 74);
            pdfDocument.AddFormField(new PdfTextField("arrivalDate", 2, fieldLeft, 74, 120, 22)
            {
                Font = fieldFont,
                BorderColor = borderColor,
                BorderStyle = model.BorderStyle,
                Description = "Arrival date"
            });

            if (model.AddDocumentScript && !pdfA)
            {
                // The document level script defines the functions used by the scripts of the fields.
                // The script does not change the document when it is opened
                pdfDocument.AddJavaScript("function isValidEmail(value) { return value.length == 0 || value.indexOf('@') > 0; }");
            }

            byte[] outPdfBuffer = pdfDocument.Save();

            FileResult fileResult = new FileContentResult(outPdfBuffer, "application/pdf");
            fileResult.FileDownloadName = "Create_PDF_Forms_from_Code.pdf";
            return fileResult;
        }

        private static void AddLabel(PdfDocument pdfDocument, string text, PdfFont font, float yPos)
        {
            pdfDocument.AddText(new PdfTextElement(text, font) { X = 0, Y = yPos + 4 });
        }

        private static bool PdfStandardIsPdfA(PdfStandard pdfStandard)
        {
            return pdfStandard.ToString().Contains("PdfA");
        }

        private string GetDemoFilesPath() => m_hostingEnvironment.ContentRootPath + "/wwwroot" + "/DemoAppFiles/Input/";
        private string GetDemoFontsPath() => Path.Combine(GetDemoFilesPath(), "Font_Files");
    }
}

See Also