Make the third Column invisibly and Retrieve value

See more:

C#

WPF

Goal:
Display two column without displaying the third column inside of richtextbox

and

the third column shall not take any space in the richtextbox. You should only see two column and in reality it is three column inside of richtextbox.


Problem:
When I want to retrieve the value from the table, I also should retrieve value from third column.
The main problem is how to do it?
I have tried it but failed. I do not know what syntax code is needed.

private void Window_Loaded(object sender, RoutedEventArgs e)
  {

   var tab = new Table();
   tab.Name = "MyTable";
   newRtb.RegisterName("MyTable", tab);


   var gridLenghtConvertor = new GridLengthConverter();

   tab.Columns.Add(new TableColumn() { Name = "Column1", Width = (GridLength)gridLenghtConvertor.ConvertFromString("*") });
   tab.Columns.Add(new TableColumn() { Name = "Column2", Width = (GridLength)gridLenghtConvertor.ConvertFromString("*") });

   tab.RowGroups.Add(new TableRowGroup());

   for (int i = 0; i < 10; i++)
   {
    TableRow tr = new TableRow();
    tr.MouseLeftButtonDown += tr_MouseLeftButtonDown;
    tab.RowGroups[0].Rows.Add(tr);
    var tabRow = tab.RowGroups[0].Rows[i];

    tabRow.Cells.Add(new TableCell(new Paragraph(new Run("Row" + (i + 1).ToString() + " Column1"))) { TextAlignment = TextAlignment.Center });
    tabRow.Cells.Add(new TableCell(new Paragraph(new Run("Row" + (i + 1).ToString() + " Column2"))));
   }


   newRtb.Document.Blocks.Add(tab);
  }

  private void tr_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
  {
   //reset background of all rows:
   Table table = newRtb.FindName("MyTable") as Table;
   foreach (TableRow row in table.RowGroups[0].Rows)
   {
    row.Background = Brushes.Transparent;
   }

   //set background of selected row:
   TableRow tr = sender as TableRow;
   tr.Background = Brushes.SpringGreen;

   //get value of second cell:
   Paragraph p = tr.Cells[1].Blocks.FirstBlock as Paragraph;
   Run run = p.Inlines.FirstInline as Run;
   string text = run.Text;
  }

private void btn_test_Click(object sender, RoutedEventArgs e)
        {
            Table table = newRtb.FindName("MyTable") as Table;
            foreach (TableRow row in table.RowGroups[0].Rows)
            {
                if (row.Background == Brushes.SpringGreen)
                {
                    //get value of second cell:
                    Paragraph p = row.Cells[1].Blocks.FirstBlock as Paragraph;
                    Run run = p.Inlines.FirstInline as Run;
                    MessageBox.Show("Second cell value: " + run.Text);
                }
            }
        }