How to Looping through the XML document

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Xml;

namespace DemoClass
{
  public partial class Form1 : Form
  {
    public Form1()
    {
      InitializeComponent();
    }

    private void button1_Click(object sender, EventArgs e)
    {
      XmlDocument document = new XmlDocument();
      document.Load("Products.xml");
      Textbox1.Text = FormatTextArea(document.DocumentElement as XmlNode, "", "");
    }

    private string FormatTextArea(XmlNode node, string textMark, string indent)
    {
      if (node is XmlText)
      {
        textMark += node.Value;
        return textMark;
      }

      if (string.IsNullOrEmpty(indent))
        indent = "";
      else
      {
        textMark += "\r\n" + indent;
      }

      if (node is XmlComment)
      {
        textMark += node.OuterXml;
        return textMark;
      }

      textMark += "<" + node.Name;
      if (node.Attributes.Count > 0)
      {
        AddAttributes(node, ref textMark);
      }
      if (node.HasChildNodes)
      {
        textMark += ">";
        foreach (XmlNode child in node.ChildNodes)
        {
          textMark = FormatText(child, textMark, indent + "  ");
        }
        if (node.ChildNodes.Count == 1 &&
           (node.FirstChild is XmlText || node.FirstChild is XmlComment))
          textMark += "</" + node.Name + ">";
        else
          textMark += "\r\n" + indent + "</" + node.Name + ">";
      }
      else
        textMark += " />";
      return textMark;
    }
    private void AddAttributes(XmlNode node, ref string textref)
    {
      foreach (XmlAttribute xaAttr in node.Attributes)
      {
        textref += " " + xaAttr.Name + "='" + xaAttr.Value + "'";
      }
    }
  }
}