test.cs

[HttpGet]
public List<SmartFormField> GetFormFields(string filename) {

   // read all acroform fields from PDF document
   TXTextControl.DocumentServer.PDF.AcroForms.FormField[] formFields =
      TXTextControl.DocumentServer.PDF.Forms.GetAcroFormFields("App_Data/" + filename);

   List<SmartFormField> smartFormFields = new List<SmartFormField>();

   // loop through all fields and convert them to "SmartFormField" objects
   foreach (TXTextControl.DocumentServer.PDF.AcroForms.FormField field in formFields) {

      switch (field) {
         case FormTextField textField:
            smartFormFields.Add(new SmartTextFormField() {
               Name = textField.FieldName,
               Text = textField.Value,
               DisplayName = textField.AlternateFieldName
            });
            break;
         case TXTextControl.DocumentServer.PDF.AcroForms.FormCheckBox checkBoxField:
            smartFormFields.Add(new SmartCheckboxField() {
               Name = checkBoxField.FieldName,
               Checked = checkBoxField.IsChecked,
               DisplayName = checkBoxField.AlternateFieldName
            });
            break;
         case FormComboBox comboBoxField:
            SmartDropdownField sddf = new SmartDropdownField() {
               Name = comboBoxField.FieldName,
               Text = comboBoxField.Value,
               DisplayName = comboBoxField.AlternateFieldName
            };

            foreach (var item in comboBoxField.Options) {
               sddf.Items.Add(item);
            }

            smartFormFields.Add(sddf);

            break;
      }

   }

   // return fields
   return smartFormFields;
}