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];
                }
            }

上面的代码适用于大多数rss提要但我在进行最后一个循环时遇到了nullrefrence异常。我该怎么做才能让它发挥作用？

Answer 1

您的循环代码不在try块内。您应该首先更改它，然后您应该使用XDocument和ForEach。另外看看@MichaelKjörling所写的内容。

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");
}

Answer 2

为什么重新发明轮子？

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

......应该做的伎俩。（我很确定RSS只允许在根channel元素中使用单个rss元素。否则，请查看SelectNodes()而不是SelectSingleNode()。）

在读取rss的xml文件时获取null引用异常

2 个答案: