test.cs

using (ServerTextControl tx = new ServerTextControl()) {
  tx.Create();
  tx.Load("patient_history.tx", StreamType.InternalUnicodeFormat);

   using (MailMerge mailMerge = new MailMerge()) {
      mailMerge.TextComponent = tx;

      if (flatten == false)
         mailMerge.FormFieldMergeType = FormFieldMergeType.Preselect;
      else
         mailMerge.FormFieldMergeType = FormFieldMergeType.Replace;

      mailMerge.RemoveEmptyBlocks = false;

      string jsonData = System.IO.File.ReadAllText("patient-data.json");
      mailMerge.MergeJsonData(jsonData);
	}

   // export to PDF
   tx.Save("results.pdf", StreamType.InternalUnicodeFormat);
}