新手，请教大牛 。winfrom统计 xml文件

Question

想用winform统计了FriendlyName节点中出现名字的次数，结果过为
吴    四  1
张二一    1
孟　一    2
龚　三    1
xml文件格式如下：<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type='text/xsl' href='ChatRecord.xsl'?>
<Log ChatType="2" Caption="考核【144752】 的对话历史记录" OwnerUid="2662494" Id="45636" Upload="false" ChatRecordIndex="1">
<Message ID="1" SessionID="1" Date="2012-08-08" Time="11:03:59" FromUid="2662494">
<From>
<User FriendlyName="吴    四"/>
</From>
<To>
<User FriendlyName=""/>
</To>
<Text>&lt;span style="font-family:宋体;font-size:11pt;font-weight:normal;font-style:normal;text-decoration:none;color:#000000;"&gt;??/&lt;/span&gt;</Text>
</Message>
<Message ID="2" SessionID="1" Date="2012-08-08" Time="11:04:02" FromUid="2662491">
<From>
<User FriendlyName="孟　一"/>
</From>
<To>
<User FriendlyName=""/>
</To>
<Text>&lt;span style="font-family:宋体;font-size:11pt;font-weight:normal;font-style:normal;text-decoration:none;color:#000000;"&gt;&lt;IMG  onclick=javascript:ClickEvent(this); type="0" src="C:\Program Files\imo\i'm office\AppData\Emotion\204.gif" realwidth="0" realheight="0" onload="javascript:if(typeof(ImgOnLoad) == &amp;apos;function&amp;apos;){ImgOnLoad(this);}" &gt;&lt;/span&gt;</Text>
</Message>
<Message ID="3" SessionID="2" Date="2012-08-08" Time="11:04:19" FromUid="2662480">
<From>
<User FriendlyName="张二一"/>
</From>
<To>
<User FriendlyName=""/>
</To>
<Text>&lt;span style="font-family:宋体;font-size:11pt;font-weight:normal;font-style:normal;text-decoration:none;color:#000000;"&gt;体验一下效果&lt;/span&gt;</Text>
</Message>
<Message ID="4" SessionID="1" Date="2012-08-08" Time="11:04:47" FromUid="2662491">
<From>
<User FriendlyName="孟　一"/>
</From>
<To>
<User FriendlyName=""/>
</To>
<Text>&lt;span style="font-family:宋体;font-size:11pt;font-weight:normal;font-style:normal;text-decoration:none;color:#000000;"&gt;效果很好很强大。。&lt;/span&gt;</Text>
</Message>
<Message ID="355" SessionID="27" Date="2012-12-25" Time="09:29:49" FromUid="2662486">
<From>
<User FriendlyName="龚　三"/>
</From>
<To>
<User FriendlyName=""/>
</To>
<Text>&lt;span style="font-family:宋体;font-size:21pt;font-weight:normal;font-style:normal;text-decoration:none;color:#ff0000;"&gt;&lt;IMG  onclick=javascript:ClickEvent(this); type="0" src="C:\Program Files\imo\i'm office\AppData\Emotion\120.gif" realwidth="0" realheight="0" onload="javascript:if(typeof(ImgOnLoad) == &amp;apos;function&amp;apos;){ImgOnLoad(this);}" &gt;&lt;/span&gt;</Text>
</Message>
</Log>

Answer 1

菜鸟给一方案：
           if (File.Exists(s_FilePath))
            {
                XElement Xdoc = XElement.Load(s_FilePath);
                Dictionary<string, int> test = Xdoc.Descendants("User")
                    .Select(s => s.Attribute("FriendlyName").Value)
                    .Where(s => !string.IsNullOrEmpty(s))
                    .GroupBy(s => s)
                    .ToDictionary(s => s.Key, s => s.Count());
            }

Answer 2

不行呢？我是新手，这个报错test = Xdoc.Descendants("User")，能解释了吗？

Answer 3

代码如下：
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Xml.Linq;
using System.Xml;
using System.Windows.Forms;namespace imo
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }        private void button1_Click(object sender, EventArgs e)
        {
            OpenFileDialog openFileDialog1 = new OpenFileDialog();     //显示选择文件对话框            openFileDialog1.InitialDirectory = "c:\\";            openFileDialog1.Filter = "xml files (*.xml)|*.xml";            openFileDialog1.FilterIndex = 2;            openFileDialog1.RestoreDirectory = true;
            //"(*.xls)|*.xls";            if (openFileDialog1.ShowDialog() == DialogResult.OK)
            {                this.textBox1.Text = openFileDialog1.FileName;          //显示文件路径            }
        }                      private void Form1_Load(object sender, EventArgs e)
        {
           
        }        private void button2_Click(object sender, EventArgs e)
        {
            XmlDocument xmlDoc = new XmlDocument();            //xmlDoc.Load(this.textBox1.Text.Trim());            if (File.Exists(this.textBox1.Text.Trim())
            {
                XElement Xdoc = XElement.Load(this.textBox1.Text.Trim());
                Dictionary<string, int> test = Xdoc.Descendants("User")
                    .Select(s => s.Attribute("FriendlyName").Value)
                    .Where(s => !string.IsNullOrEmpty(s))
                    .GroupBy(s => s)
                    .ToDictionary(s => s.Key, s => s.Count());
            }            
                     }        private void label1_Click(object sender, EventArgs e)
        {        }      
        
    }
}请大牛，帮看看红色部分，报错原因

Answer 4

修改为这个，还是不行呢？
private void button2_Click(object sender, EventArgs e)
        {
            XmlDocument xmlDoc = new XmlDocument();            //xmlDoc.Load(this.textBox1.Text.Trim());            
                XElement Xdoc = XElement.Load(this.textBox1.Text.Trim());
                Dictionary<string, int> test = xmldoc.Descendants("User")
                    .Select(s => s.Attribute("FriendlyName").Value)
                    .Where(s => !string.IsNullOrEmpty(s))
                    .GroupBy(s => s)
                    .ToDictionary(s => s.Key, s => s.Count());
            }