test.cs

FormField[] acroForms = 
    TXTextControl.DocumentServer.PDF.Forms.GetAcroFormFields("form.pdf");

foreach (FormField field in acroForms)
{ 
    switch (field)
    {
        case TXTextControl.DocumentServer.PDF.AcroForms.FormTextField textField:
            Console.WriteLine(textField.Value);
            break;

        case TXTextControl.DocumentServer.PDF.AcroForms.FormCheckBox checkBoxField:
            Console.WriteLine(checkBoxField.IsChecked);
            break;

        case TXTextControl.DocumentServer.PDF.AcroForms.FormComboBox comboBoxField:
            foreach(var item in comboBoxField.Options)
                Console.WriteLine(item);
            break;
    }
}