#region 判断某XML存不存在
        /// <summary>
        /// 判断某XML存不存在
        /// </summary>
        /// <param name="path">文件路径</param>
        /// <returns>布尔值</returns>
        public bool TheXmlIsExist(string path)
        {
            return File.Exists(path);            
        }

        #endregion

        #region  读取一个XML文件，返回一个DataSet
        /// <summary>
        /// 读取一个XML文件，返回一个DataSet
        /// </summary>
        /// <param name="path">Xml文件路径</param>
        /// <returns>把xml文件读成DataSet取出</returns>

        public DataSet ReadTheXmlAndReturnDataSet(string path)
        {
            try
            {
                DataSet ds = new DataSet();
                ds.ReadXml(path);
                return ds;
            }
            catch (Exception e)
            {
                throw e;
            }
        }

        #endregion

------解决方案--------------------
不会做，先做简单的习题。

------解决方案--------------------

[c#]

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 TreeWpf
{
   /// <summary>
   /// Window1.xaml 的交互逻辑
   /// </summary>
   ///  

   public partial class Window1 : Window
   {
       List<Info> MyInfoList = new List<Info>();
       public Window1()
       {
           InitializeComponent();
           MyInfoList = GetForumData();
           AddTreeNode(0, null);
          // MytreeView.ItemsSource = MyInfoList;

       }
       private void AddTreeNode(int parentID, TreeViewItem treeViewItem)
       {
           List<Info> result = (from forumInfo in MyInfoList
                                     where forumInfo.ParendID == parentID
                                select forumInfo).ToList<Info>();

           if (result.Count > 0)
           {
               foreach (Info Row in result)
               {
                   TreeViewItem objTreeNode = new TreeViewItem();
                   objTreeNode.Header = Row.ForumName;
                   objTreeNode.DataContext = Row;

                   //此样式将会添加的所有叶子结点上
                   //objTreeNode.ItemContainerStyle = this.Resources["RedItemStyle"] as Style;

                   //添加根节点
                   if (treeViewItem == null)
                   {
                       MytreeView.Items.Add(objTreeNode);
                   }
                   else
                   {
                       treeViewItem.Items.Add(objTreeNode);
                   }
                   AddTreeNode(Row.ForumID, objTreeNode);
               }
           }
       }
       public List<Info> GetForumData()
       {
           List<Info> forumList = new List<Info>();
           forumList.Add(new Info() { ForumID = 1, ParendID = 0, ForumName = "笔记本版块" });
           forumList.Add(new Info() { ForumID = 2, ParendID =