test.cs

private void TextControl1_TableCreated(out string dataStructure, object sender, TableEventArgs e) {
      
  List<ApplicationField> applicationFields = new List<ApplicationField>();

  // adapt the table size to the page width
  e.Table.AdaptSize(textControl1);

  // loop through all cells
  foreach (TableCell cell in e.Table.Cells) {

    // if the cell is not a formula, has a length and is not empty
    if (cell.Formula == "" &&
      cell.Length != -1 &&
      cell.Text != "" &&
      cell.CellFormat.TextType != TextType.Standard) {

      cell.Select();

      // create a new merge field
      MergeField mf = new MergeField();
      mf.Text = "«" + cell.Text + "»"; // set the field text
      cell.Text = "";

      // get the text of the previous cell in the first column
      // and make it unique by adding the column number
      var previousCellText = e.Table.Cells.GetItem(cell.Row, 1).Text + "_" + cell.Column;

      // remove spaces from previousCellText and convert to title case
      mf.Name = System.Globalization.CultureInfo.CurrentCulture.TextInfo.ToTitleCase(previousCellText.ToLower()).Replace(" ", "");

      // add the merge field to the document
      textControl1.Select(cell.Start - 1, 0);
      textControl1.ApplicationFields.Add(mf.ApplicationField);
      applicationFields.Add(mf.ApplicationField);
    }
  }

  dataStructure = GetMergeFields(applicationFields);
}

// function to return a json structure from an array of merge fields
private string GetMergeFields(List<ApplicationField> applicationFields) {
  var fields = new List<string[]>();

  foreach (ApplicationField field in applicationFields) {
    fields.Add(new string[] { field.Name, field.Text });
  }

  return JsonConvert.SerializeObject(fields);
}