这段代码出了什么问题

Question

为什么while循环没有返回任何东西？我认为这与.NET有关.我有.NET 2.0.问题是while语句将执行一次然后退出,就好像没有具有该名称的节点,当肯定存在时.

以下是XML的示例:

<rss version="2.0">
    <channel>
        <title>...</title>
        <link>...</link>
        <description>...</description>
        <lastBuildDate>...</lastBuildDate>
        <item>
            <title>User greeting</title>
            <guid>...</guid>
            <link>http://...</link>

            <description>Voicebox number: 1</description>
            <author>Free Conference Call</author>
        </item>
        <item>
            <title>User greeting</title>
            <guid>...</guid>
            <link>http://...</link>

            <description>Voicebox number: 1</description>
            <author>Free Conference Call</author>
        </item>
    </channel>
</rss>

这是代码:

HttpWebRequest webreq = (HttpWebRequest)WebRequest.Create (reqURL);
// Set some reasonable limits on resources used by this request
webreq.MaximumAutomaticRedirections = 4;
webreq.MaximumResponseHeadersLength = 4;
//====================
// Set credentials to use for this request.
webreq.Credentials = CredentialCache.DefaultCredentials;
HttpWebResponse response = (HttpWebResponse)webreq.GetResponse ();
//====================
// Get the stream associated with the response.
receiveStream = response.GetResponseStream ();
//====================
// Pipes the stream to a higher level stream reader with the required encoding format. 
readStream = new StreamReader(receiveStream, Encoding.UTF8);
resXML = readStream.ReadToEnd();
readStream = new StreamReader(receiveStream, Encoding.UTF8);
//====================
Console.WriteLine(resXML);
Stream XMLStream = receiveStream;
readStream = new StreamReader(XMLStream, Encoding.UTF8);

XmlReaderSettings settings = new XmlReaderSettings();
settings.ConformanceLevel = ConformanceLevel.Fragment;
settings.IgnoreWhitespace = true;
settings.IgnoreComments = true;
XmlReader reader = System.Xml.XmlReader.Create(readStream, settings);

while(reader.EOF == false)
{
    reader.ReadToFollowing("link");
    Console.WriteLine("link: " + reader.Value);
    //=======================================
    reader.ReadToFollowing("description");
    Console.WriteLine("descrip: " + reader.Value);
}

Answer 1

您在通话时已经阅读了响应中的所有数据

resXML = readerStream.ReadToEnd();

...... readerStream并且readStream它们都是分层的receiveStream,所以一旦你通过一个读取所有数据,你就无法通过另一个读取它.

你应该真的有一个using响应的声明 - 理想情况下涉及的各种流.鉴于您可以XmlReader从流创建一个,而不仅仅是一个StreamReader,为什么不使用这样的东西:

XmlReaderSettings settings = new XmlReaderSettings();
settings.ConformanceLevel = ConformanceLevel.Fragment;
settings.IgnoreWhitespace = true;
settings.IgnoreComments = true;

using (HttpWebResponse response = (HttpWebResponse)webreq.GetResponse())
{
   using (Stream stream = response.GetResponseStream())
   {
       using(XmlReader reader = XmlReader.Create(stream, settings))
       {
           // Do stuff here
       }
   }
}

另外,我通常建议创建一个XmlDocument或类似的东西,而不是使用XmlReader它 - 它不适用于大型文档,但它更容易使用.