Question

我想制作一个RSS阅读器，它可以同时获取多个新闻源，而不会让我的应用程序在获取源时“冻结”。为此，我希望一些代码在一个单独的线程中运行。我尝试了一些不同的东西，让它在一个单独的线程中运行，但我不断得到例外。我的代码看起来像这个atm：

namespace NewsReader
{
    public partial class Form1 : Form
    {
        XmlTextReader rssReader;

        XmlDocument rssDoc;

        XmlNode nodeRss;

        XmlNode nodeChannel;

        XmlNode nodeItem;

        ListViewItem rowNews;

        public Form1()
        {
            InitializeComponent();
        }

        private void btnRead_Click(object sender, EventArgs e)
        {

            //Creates a XmlTextReader which reads from the url entered in input field
            rssReader = new XmlTextReader(txtUrl.Text);

            //Creates an xml doc to save the content of the entered path
            rssDoc = new XmlDocument();

            //Loads the xml content from the reader into a XmlDocument
            rssDoc.Load(rssReader);


            //Make a loop to search for the <rss> tag
            for (int i = 0; i < rssDoc.ChildNodes.Count; i++)
            {
                //If the childenode is the rss tag
                if (rssDoc.ChildNodes[i].Name == "rss")
                {
                    //the <rss> tag is found, and we know where it is
                    nodeRss = rssDoc.ChildNodes[i];
                }
            }

            //Make a loop to search for the <channel> tag
            for (int i = 0; i < nodeRss.ChildNodes.Count; i++)
            {
                //If the childnode is the channel tag
                if (nodeRss.ChildNodes[i].Name == "channel")
                {
                    //The channel tag is found and we know where it is
                    nodeChannel = nodeRss.ChildNodes[i];
                }
            }

            //Make a loop to search for the <item> tag
            for (int i = 0; i < nodeChannel.ChildNodes.Count; i++)
            {
                //If the childnode is the item tag
                if (nodeChannel.ChildNodes[i].Name == "item")
                {
                    //the item tag is found, and we know where it is
                    nodeItem = nodeChannel.ChildNodes[i];

                    //Creates a new row in the LstView which contains information from inside the nodes
                    rowNews = new ListViewItem();
                    rowNews.Text = nodeItem["title"].InnerText;
                    rowNews.SubItems.Add(nodeItem["link"].InnerText);
                    lstView.Items.Add(rowNews);

                }
            }

        }
    }

}

有没有人有一些如何处理这个问题的例子？我的代码的代码示例非常感谢：）

提前致谢。

Answer 1

您可以查看BackgroundWorker课程。这是一个例子：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Windows.Forms;
using System.Xml.Linq;
using System.Xml.XPath;

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

    private void button1_Click(object sender, EventArgs e)
    {
        backgroundWorker1.RunWorkerAsync(txtUrl.Text);
    }

    private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
    {
        var rssDoc = XDocument.Load((string)e.Argument);
        var items = new List<ListViewItem>();
        foreach (var item in rssDoc.XPathSelectElements("//item"))
        {
            var listItem = new ListViewItem();
            listItem.Text = item.Element("title").Value;
            listItem.SubItems.Add(item.Element("link").Value);
            items.Add(listItem);
        }
        e.Result = items.ToArray();
    }

    private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        lstView.Items.AddRange((ListViewItem[])e.Result);
    }
}

Answer 2

如果您使用的是.net 4.0，则可以使用Task系统获得更简单的方法，并可能获得更好的性能。

  foreach (var item in rssDoc.XPathSelectElements("//item"))
  {
    Task fetch = new Task(() =>
    {
     // Go to server and get data....
     // Add Data to UI...
    });

    fetch.Start();
  }

这里的主要好处是任务系统将决定如何以及何时运行每个获取操作。理论上，每个操作都将在其自己的线程中运行，因此一次一个或多个将处于活动状态，而不仅仅是您在正常循环中看到的一个。系统足够好，可以为你做一些负载平衡。

Answer 3

如果您使用的是.NET 3.5或更高版本，则可以使用SyndicationFeed类型来轻松解析RSS源。

我正在调整Darin Dimitrov的代码示例：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Windows.Forms;
using System.ServiceModel.Syndication;
using System.Xml.Linq;
using System.Xml.XPath;

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

    private void button1_Click(object sender, EventArgs e)
    {
        backgroundWorker1.RunWorkerAsync(txtUrl.Text);
    }

    private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
    {
        var reader = new XmlTextReader((string)e.Argument);
        var feed = SyndicationFeed.Load(reader);
        var items = new List<ListViewItem>();
        foreach (var item in feed.Items)
        {
            var listItem = new ListViewItem();
            listItem.Text = item.Title;
            foreach (var link in item.Links)
            {
                listItem.SubItems.Add(link.Uri.AbsoluteUri);
            }
            items.Add(listItem);
        }
        e.Result = items.ToArray();
    }

    private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        lstView.Items.AddRange((ListViewItem[])e.Result);
    }
}

RSS阅读器多线程C＃

3 个答案: