class PdfInteractiveFormTextFieldExample
{
    /// <summary>
    /// Creates a PDF document with numeric text field.
    /// </summary>
    /// <param name="filename">The filename.</param>
    public static void CreateDocumentWithNumericTextField(string filename)
    {
        // create PDF document
        using (Vintasoft.Imaging.Pdf.PdfDocument document = new Vintasoft.Imaging.Pdf.PdfDocument())
        {
            // create interactive form in PDF document
            document.InteractiveForm = 
                new Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfDocumentInteractiveForm(document);
            
            // specify that the viewer application must construct appearance streams and
            // appearance properties for all widget annotations
            document.InteractiveForm.NeedAppearances = true;
            
            // create an empty page
            Vintasoft.Imaging.Pdf.Tree.PdfPage page = new Vintasoft.Imaging.Pdf.Tree.PdfPage(
                document, Vintasoft.Imaging.PaperSizeKind.A4);
            // add page to the document
            document.Pages.Add(page);
            
            float width = 100;
            float height = 25;
            // create a rectangle that defines the field position on PDF page
            System.Drawing.RectangleF rect = new System.Drawing.RectangleF(
                (page.Size.Width - width) / 2,
                ((page.Size.Height - height) / 3) * 2,
                width, height);
            
            // create a text field
            Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormTextField textField =
                new Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormTextField(
                    document, "NumericField", rect, "12345");
            
            // create the text value validation method that accepts numbers (0-9 digits) only
            string javaScriptCode = 
                "var regex = /[^0-9]/;if(regex.test(event.change)) event.change = '';";
            Vintasoft.Imaging.Pdf.Tree.PdfJavaScriptAction action = 
                new Vintasoft.Imaging.Pdf.Tree.PdfJavaScriptAction(document, javaScriptCode);
            textField.AdditionalActions = 
                new Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormFieldAdditionalActions(document);
            // set the validation action for the AdditionalActions.Keystroke trigger event
            textField.AdditionalActions.Keystroke = action;
            
            // set the default appearance of text
            Vintasoft.Imaging.Pdf.Tree.Fonts.PdfFont font = document.FontManager.GetStandardFont(
                Vintasoft.Imaging.Pdf.Tree.Fonts.PdfStandardFontType.TimesRoman);
            textField.SetTextDefaultAppearance(font, 12, System.Drawing.Color.Black);
            
            // set the border style
            textField.Annotation.BorderStyle = new Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationBorderStyle(document);
            textField.Annotation.BorderStyle.Style = Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationBorderStyleType.Inset;
            textField.Annotation.BorderStyle.Width = 1;
            
            // set the appearance characteristics
            textField.Annotation.AppearanceCharacteristics = 
                new Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationAppearanceCharacteristics(document);
            textField.Annotation.AppearanceCharacteristics.BorderColor = System.Drawing.Color.Gray;
            
            // add the text field to the interactive form of document
            document.InteractiveForm.Fields.Add(textField);
            
            // add annotation, associated with the text field, to the page
            page.Annotations = new Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationList(document);
            page.Annotations.Add(textField.Annotation);
            
            // save the document
            document.Save(filename);
        }
    }
}