/// <summary>
/// Creates a PDF document with calculated interactive form field.
/// </summary>
/// <param name="filename">The filename.</param>
public static void CreateDocumentWithCalculatedInteractiveFormField(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;

        // font and font size
        float fontSize = 12;
        Vintasoft.Imaging.Pdf.Tree.Fonts.PdfFont font = 
            document.FontManager.GetStandardFont(Vintasoft.Imaging.Pdf.Tree.Fonts.PdfStandardFontType.TimesRoman);

        // 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 = 60;
        float height = 40;
        // create a rectangle that defines the object (first field) position on PDF page
        System.Drawing.RectangleF rect = new System.Drawing.RectangleF(
            (page.Size.Width - width * 5) / 2,
            ((page.Size.Height - height) / 3) * 2,
            width, height);

        // open PdfGraphics on page
        using (Vintasoft.Imaging.Pdf.Drawing.PdfGraphics graphics = page.GetGraphics())
        {
            // create calculator field: group of three fields
            Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormField calculator =
                new Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormField(document, "Calculator");
            calculator.SetTextDefaultAppearance(font, fontSize * 1.5f, System.Drawing.Color.Black);
            calculator.TextQuadding = Vintasoft.Imaging.Pdf.Tree.InteractiveForms.TextQuaddingType.Centered;

            // create the border style
            Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationBorderStyle borderStyle = 
                new Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationBorderStyle(document);
            borderStyle.Style = Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationBorderStyleType.Inset;
            borderStyle.Width = 1;

            // create the appearance characteristics
            Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationAppearanceCharacteristics appearanceCharacteristics =
                new Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationAppearanceCharacteristics(document);
            appearanceCharacteristics.BorderColor = System.Drawing.Color.Gray;

            // create the left text box
            Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormTextField textField =
                new Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormTextField(document, "Left", rect, "2");
            textField.DefaultValue = textField.Value;
            textField.Annotation.BorderStyle = borderStyle;
            textField.Annotation.AppearanceCharacteristics = appearanceCharacteristics;
            // add the left text box to the calculator
            calculator.Kids.Add(textField);

            // update the rectangle that defines the object position on PDF page
            rect.X += rect.Width;

            // draw the symbol '+' on the page
            graphics.DrawString("+", font, fontSize * 1.5f,
                new Vintasoft.Imaging.Pdf.Drawing.PdfBrush(System.Drawing.Color.Black), rect, 
                Vintasoft.Imaging.Pdf.Drawing.PdfContentAlignment.Center, false);

            // update the rectangle that defines the object position on PDF page
            rect.X += rect.Width;

            // create the right text box
            textField = new Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormTextField(document, "Right", rect, "3");
            textField.DefaultValue = textField.Value;
            textField.Annotation.BorderStyle = borderStyle;
            textField.Annotation.AppearanceCharacteristics = appearanceCharacteristics;
            // add the right text box to the calculator
            calculator.Kids.Add(textField);

            // update the rectangle that defines the object position on PDF page
            rect.X += rect.Width;

            // draw the symbol '=' on the page
            graphics.DrawString("=", font, fontSize * 1.5f,
                new Vintasoft.Imaging.Pdf.Drawing.PdfBrush(System.Drawing.Color.Black), rect, 
                Vintasoft.Imaging.Pdf.Drawing.PdfContentAlignment.Center, false);

            // create the calculator program written on JavaScript
            System.Text.StringBuilder javaScriptCode = new System.Text.StringBuilder();
            javaScriptCode.Append("var left = this.getField('Calculator.Left');");
            javaScriptCode.Append("var right = this.getField('Calculator.Right');");
            javaScriptCode.Append("var result = this.getField('Calculator.Result');");
            javaScriptCode.Append("result.value = left.value + right.value;");
            Vintasoft.Imaging.Pdf.Tree.PdfJavaScriptAction calculatorProgram =
                new Vintasoft.Imaging.Pdf.Tree.PdfJavaScriptAction(document, javaScriptCode.ToString());

            // update the rectangle that defines the object position on PDF page
            rect.X += rect.Width;

            // create the result text box
            textField = new Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormTextField(document, "Result", rect);
            textField.IsReadOnly = true;
            textField.Annotation.BorderStyle = borderStyle;
            textField.Annotation.AppearanceCharacteristics = appearanceCharacteristics;
            // set a program that will calculate value of result field
            textField.AdditionalActions = 
                new Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormFieldAdditionalActions(document);
            textField.AdditionalActions.Calculate = calculatorProgram;
            // specify that calcualtor program must be executed when page is opened
            textField.Annotation.AdditionalActions.PageOpen = calculatorProgram;
            // add the result text box to the calculator
            calculator.Kids.Add(textField);

            // add result field to the calculated fields (calcualtion order)
            // of the document interactive form fields
            document.InteractiveForm.CalculationOrder = 
                new Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormFieldList(document);
            document.InteractiveForm.CalculationOrder.Add(textField);

            // add field group to the document
            document.InteractiveForm.Fields.Add(calculator);

            // add annotations, associated with field group, to the page
            page.Annotations = new Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationList(document);
            page.Annotations.AddRange(calculator.GetAnnotations());

            // update appearance of field group
            calculator.UpdateAppearance();
        }

        // save the document
        document.Save(filename);
    }
}

''' <summary>
''' Creates a PDF document with calculated interactive form field.
''' </summary>
''' <param name="filename">The filename.</param>
Public Shared Sub CreateDocumentWithCalculatedInteractiveFormField(filename As String)
    ' create PDF document
    Using document As 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

        ' font and font size
        Dim fontSize As Single = 12
        Dim font As Vintasoft.Imaging.Pdf.Tree.Fonts.PdfFont = document.FontManager.GetStandardFont(Vintasoft.Imaging.Pdf.Tree.Fonts.PdfStandardFontType.TimesRoman)

        ' create an empty page
        Dim page As New Vintasoft.Imaging.Pdf.Tree.PdfPage(document, Vintasoft.Imaging.PaperSizeKind.A4)
        ' add page to the document
        document.Pages.Add(page)

        Dim width As Single = 60
        Dim height As Single = 40
        ' create a rectangle that defines the object (first field) position on PDF page
        Dim rect As New System.Drawing.RectangleF((page.Size.Width - width * 5) / 2, ((page.Size.Height - height) / 3) * 2, width, height)

        ' open PdfGraphics on page
        Using graphics As Vintasoft.Imaging.Pdf.Drawing.PdfGraphics = page.GetGraphics()
            ' create calculator field: group of three fields
            Dim calculator As New Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormField(document, "Calculator")
            calculator.SetTextDefaultAppearance(font, fontSize * 1.5F, System.Drawing.Color.Black)
            calculator.TextQuadding = Vintasoft.Imaging.Pdf.Tree.InteractiveForms.TextQuaddingType.Centered

            ' create the border style
            Dim borderStyle As New Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationBorderStyle(document)
            borderStyle.Style = Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationBorderStyleType.Inset
            borderStyle.Width = 1

            ' create the appearance characteristics
            Dim appearanceCharacteristics As New Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationAppearanceCharacteristics(document)
            appearanceCharacteristics.BorderColor = System.Drawing.Color.Gray

            ' create the left text box
            Dim textField As New Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormTextField(document, "Left", rect, "2")
            textField.DefaultValue = textField.Value
            textField.Annotation.BorderStyle = borderStyle
            textField.Annotation.AppearanceCharacteristics = appearanceCharacteristics
            ' add the left text box to the calculator
            calculator.Kids.Add(textField)

            ' update the rectangle that defines the object position on PDF page
            rect.X += rect.Width

            ' draw the symbol '+' on the page
            graphics.DrawString("+", font, fontSize * 1.5F, New Vintasoft.Imaging.Pdf.Drawing.PdfBrush(System.Drawing.Color.Black), rect, Vintasoft.Imaging.Pdf.Drawing.PdfContentAlignment.Center, _
                False)

            ' update the rectangle that defines the object position on PDF page
            rect.X += rect.Width

            ' create the right text box
            textField = New Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormTextField(document, "Right", rect, "3")
            textField.DefaultValue = textField.Value
            textField.Annotation.BorderStyle = borderStyle
            textField.Annotation.AppearanceCharacteristics = appearanceCharacteristics
            ' add the right text box to the calculator
            calculator.Kids.Add(textField)

            ' update the rectangle that defines the object position on PDF page
            rect.X += rect.Width

            ' draw the symbol '=' on the page
            graphics.DrawString("=", font, fontSize * 1.5F, New Vintasoft.Imaging.Pdf.Drawing.PdfBrush(System.Drawing.Color.Black), rect, Vintasoft.Imaging.Pdf.Drawing.PdfContentAlignment.Center, _
                False)

            ' create the calculator program written on JavaScript
            Dim javaScriptCode As New System.Text.StringBuilder()
            javaScriptCode.Append("var left = this.getField('Calculator.Left');")
            javaScriptCode.Append("var right = this.getField('Calculator.Right');")
            javaScriptCode.Append("var result = this.getField('Calculator.Result');")
            javaScriptCode.Append("result.value = left.value + right.value;")
            Dim calculatorProgram As New Vintasoft.Imaging.Pdf.Tree.PdfJavaScriptAction(document, javaScriptCode.ToString())

            ' update the rectangle that defines the object position on PDF page
            rect.X += rect.Width

            ' create the result text box
            textField = New Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormTextField(document, "Result", rect)
            textField.IsReadOnly = True
            textField.Annotation.BorderStyle = borderStyle
            textField.Annotation.AppearanceCharacteristics = appearanceCharacteristics
            ' set a program that will calculate value of result field
            textField.AdditionalActions = New Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormFieldAdditionalActions(document)
            textField.AdditionalActions.Calculate = calculatorProgram
            ' specify that calcualtor program must be executed when page is opened
            textField.Annotation.AdditionalActions.PageOpen = calculatorProgram
            ' add the result text box to the calculator
            calculator.Kids.Add(textField)

            ' add result field to the calculated fields (calcualtion order)
            ' of the document interactive form fields
            document.InteractiveForm.CalculationOrder = New Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormFieldList(document)
            document.InteractiveForm.CalculationOrder.Add(textField)

            ' add field group to the document
            document.InteractiveForm.Fields.Add(calculator)

            ' add annotations, associated with field group, to the page
            page.Annotations = New Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationList(document)
            page.Annotations.AddRange(calculator.GetAnnotations())

            ' update appearance of field group
            calculator.UpdateAppearance()
        End Using

        ' save the document
        document.Save(filename)
    End Using
End Sub