读取 rss 的 xml 文件时获取空引用异常

Question

            try
            {
                rssDoc = new XmlDocument();
                // Load the XML context into XmlDocument
                rssDoc.Load(rssReader);
                MessageBox.Show(rssDoc.ToString());
            }
            catch (Exception ex)
            {
               errorProvider1.SetError(url, "Cannot load the RSS from this url");
            }
            // Loop for <rss> tag in xmldocument
            for (int i = 0; i < rssDoc.ChildNodes.Count; i++)
            {
                // If <rss> tag found
                if (rssDoc.ChildNodes[i].Name == "rss")
                {
                    // assign the <rss> tag node to nodeRSS
                    nodeRss = rssDoc.ChildNodes[i];
                }
            }
            //Loop for the <channel> tag in side <rss> tag stored in nodeRss
            for (int i = 0; i < nodeRss.ChildNodes.Count; i++)  <<<<<<EXCEPTION
            {
                // <channel> node found
                if (nodeRss.ChildNodes[i].Name == "channel")
                {
                    //assign the <channel> tag to nodeChannel 
                    nodeChannel = nodeRss.ChildNodes[i];
                }
            }

上面的代码对于大多数 rss 提要都运行良好，但我在完成最后一个循环时收到空引用异常。我应该怎么做才能让它工作？

Answer 1

为什么要重新发明轮子？

XmlNode nodeChannel = rssDoc.SelectSingleNode("/rss/channel");

。应该做这个伎俩。（我很确定 RSS 只允许根元素内的单个channel元素rss。否则，请查看SelectNodes()而不是SelectSingleNode()。

Answer 2

您的循环代码不在 try 块内。你应该先改变这一点，然后你应该使用XDocument和ForEach。也看看@Michael约林写了什么。

try
{
    XDocument rssDoc = new XDocument(rssReader);
    foreach(var ele in rssDoc.Elemtens["rss"])
    {

    }
    foreach(var ele in rssDoc.Elemtens["channel"])
    {

    }
}    
catch (Exception ex)
{
    errorProvider1.SetError(url, "Cannot load the RSS from this url");
}