class PdfInteractiveFormComboBoxFieldExample
{
    /// <summary>
    /// Creates a PDF document with the combo box fields.
    /// </summary>
    /// <param name="filename">The filename.</param>
    public static void CreateDocumentWithComboBoxField(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 = 70;
            float height = 20;
            // create a rectangle that defines check box 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 combo box field
            Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormComboBoxField comboBox = 
                new Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormComboBoxField(
                    document, "ComboBox1", rect, new string[] { "Item1", "Item2", "Item3" });
            // set the selected item
            comboBox.SelectedItem = "Item2";
            // set the defaul selected item
            comboBox.DefaultSelectedItem = comboBox.SelectedItem;
            
            // set the border style
            comboBox.Annotation.BorderStyle = 
                new Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationBorderStyle(document);
            comboBox.Annotation.BorderStyle.Style = 
                Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationBorderStyleType.Beveled;
            comboBox.Annotation.BorderStyle.Width = 1;
            
            // set the appearance characteristics
            comboBox.Annotation.AppearanceCharacteristics = 
                new Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationAppearanceCharacteristics(document);
            comboBox.Annotation.AppearanceCharacteristics.BorderColor = System.Drawing.Color.Gray;
            
            // sets the default appearance of text
            Vintasoft.Imaging.Pdf.Tree.Fonts.PdfFont font = document.FontManager.GetStandardFont(
                Vintasoft.Imaging.Pdf.Tree.Fonts.PdfStandardFontType.TimesRoman);
            comboBox.SetTextDefaultAppearance(font, 12, System.Drawing.Color.Black);
            
            // add combo box field to the interactive form of document
            document.InteractiveForm.Fields.Add(comboBox);
            
            // add annotation, associated with combobox field, to the page
            page.Annotations = new Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationList(document);
            page.Annotations.Add(comboBox.Annotation);
            
            // save the document
            document.Save(filename);
        }
    }
}