WPF(Binding of RelativeSource)

<Window x:Class="TestOfRelativeSource.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" mc:Ignorable="d" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" Height="350" Width="525">
    <Grid x:Name="g1" Background="Red" Margin="10">
        <DockPanel x:Name="d1" Background="Orange"
                   Margin="10" >
            <Grid x:Name="g2" Background="Yellow"
                  Margin="10" >
                <DockPanel x:Name="d2" Background="LawnGreen" 
                           Margin="10" >
                    <TextBox x:Name="textBox1" 
                             FontSize="24" Margin="10" />
                </DockPanel>
            </Grid>
        </DockPanel>
         
    </Grid>
</Window>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace TestOfRelativeSource
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();

            //RelativeSource rs = new RelativeSource(RelativeSourceMode.FindAncestor);
            //rs.AncestorLevel = 1;
            //rs.AncestorType = typeof (Grid);
            //Binding binding = new Binding("Name")
            //{
            //    RelativeSource = rs
            //};
            //this.textBox1.SetBinding(TextBox.TextProperty, binding);

            //RelativeSource rs = new RelativeSource();
            //rs.AncestorLevel = 2;
            //rs.AncestorType = typeof (DockPanel);
            //Binding binding = new Binding("Name")
            //{
            //    RelativeSource = rs
            //};
            //this.textBox1.SetBinding(TextBox.TextProperty, binding);

            this.textBox1.SetBinding(TextBox.TextProperty, new Binding("Name")
                        {
                            RelativeSource = new RelativeSource()
                                                {
                                                    Mode = RelativeSourceMode.Self
                                                }
                        });
        }
    }
}