C#实现简易RSS

代码如下，欢迎指正

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

namespace FinallyDemo
{
    public partial class frmRSS : Form
    {
        public frmRSS()
        {
            InitializeComponent();
        }
        string url = "";
        string xmlFilePath = "";
        XmlDocument doc = new XmlDocument();
        TreeNode tnroot = new TreeNode();
        public void DownLoadXml(string url)
        {
            if(File.Exists(xmlFilePath))
            {
                File.Delete(xmlFilePath);
            }
            WebClient wc = new WebClient();
            try
            {
                wc.DownloadFile(url, xmlFilePath);
            }
            catch (System.Exception ex)
            {
                MessageBox.Show(ex.ToString());
            }
            
        }

        public void LoadXml()
        {
            if(File.Exists(xmlFilePath))
            {
               
                doc.Load(xmlFilePath);
                XmlNode firstNode = doc.DocumentElement.FirstChild;
                XmlNode root = firstNode.FirstChild;
                treeView1.Nodes.Add(root.InnerText);
                tnroot = treeView1.Nodes[0];
            }
        }

        class Test
        {
           public string title;
            public string url;
            public Test()
            {
                
            }    
            public Test(string title,string url)
            {
                this.title = title;
                this.url = url;
            }           
        }

        Dictionary<string, Test> dictionarys = new Dictionary<string, Test>();

        public void LoadTreeTitle()
        {
            doc.Load(xmlFilePath);
            XmlNode first = doc.DocumentElement.FirstChild;

            tnroot.Nodes.Clear();

            foreach (XmlNode node in first.ChildNodes)
            {
                if(node.Name=="item")
                {
                    Test test = new Test();
                    TreeNode tn = new TreeNode();
                    foreach (XmlNode n in node)
                    {
                       switch(n.Name)
                       {
                           case "title":
                               test.title = n.InnerText;
                               break;
                           case "link":
                               test.url=n.InnerText;
                               break;
                       }
                    }
                    tn.Text=test.title;
                    tnroot.Nodes.Add(tn);
                    
                    try
                    {
                        dictionarys.Add(test.title,test);  
                    }
                    catch (System.Exception ex)
                    {
                        
                    }                               
                    
                }
            }

        }

        private void frmRSS_Load(object sender, EventArgs e)
        {
            string path = "http://www.cnblogs.com/yeszlr/rss";
            string filepaht = Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().CodeBase) + @"\test.xml";
            xmlFilePath = filepaht.Substring(6, filepaht.Length - 6);
            DownLoadXml(path);
            LoadXml();
            LoadTreeTitle();
        }

        private void treeView1_AfterSelect(object sender, TreeViewEventArgs e)
        {
            if (treeView1.SelectedNode.Nodes.Count > 0)
            {
                LoadTreeTitle();
            }
            else
            {
                string title = treeView1.SelectedNode.Text;
                foreach (Test t in dictionarys.Values)
                {
                    if (t.title == title)
                    {
                        url = t.url;
                    }
                }

                if (url != "")
                {
                    webBrowser1.Navigate(url);
                }

            }
        }
    }
}