Unity C#解析Steam新闻页提取图片URL：返回数据异常

尝试解析Steam新闻RSS中带图片链接的<enclosure>标签时遇到问题，目标是Steam应用1348750的英文US区新闻feed。用Unity的UnityWebRequest.Get获取数据，不管是取UTF-8字符串还是原始byte[]，保存到文件或打印时数据都出现混乱。原以为返回的是XHTML格式，但不知道如何转成可读格式来解析图片URL。

<item>
      <title>Update v1.3</title>
      <description>Changelog:&lt;br&gt;&lt;ul class=&quot;bb_ul&quot;&gt;&lt;li&gt;Arry and Miri can now gain affection.&lt;br&gt;&lt;/li&gt;&lt;li&gt;The player can now view Arry and Miri's epilogue scenes. (You will have to answer their proposal one more time.)&lt;br&gt;&lt;/li&gt;&lt;li&gt;The Arry and Miri achievements have been fixed and should unlock when you reach the epilogue.&lt;br&gt;&lt;/li&gt;&lt;li&gt;The ability management backend has been 100% REDONE, and all associated bugs should be fixed.&lt;br&gt;&lt;/li&gt;&lt;li&gt;Specifically, ability use counts and levels will no longer reset if they're no longer in a player preset.&lt;/li&gt;&lt;/ul&gt;&lt;br&gt;&lt;div class=&quot;bb_h2&quot;&gt;ACTION REQUIRED:&lt;/div&gt;If you take one thing from this update, it's that &lt;b&gt;Arry and Miri's&lt;/b&gt; conversation lines were &lt;b&gt;broken&lt;/b&gt; before this update, with all their epilogue scenes being &lt;b&gt;hidden&lt;/b&gt;. &lt;br&gt;&lt;br&gt;&lt;b&gt;If you've been stuck at their proposal, doing it one more time should unlock their achievements and lead you to their epilogue scenes.&lt;/b&gt;&lt;br&gt;&lt;br&gt;Additionally, I've begun work on the logbook! It's coming along nicely.&lt;br&gt;&lt;br&gt;&lt;img src=&quot;https://i.imgur.com/FBdDow9.png&quot; /&gt;</description>
      <link><![CDATA[https://store.steampowered.com/news/app/1348750/view/3178989079011859448]]></link>
      <pubDate>Tue, 10 May 2022 02:28:06 +0000</pubDate>
      <author>niku_treat</author>
      <guid isPermaLink="true">https://store.steampowered.com/news/app/1348750/view/3178989079011859448</guid>
      <enclosure url="https://cdn.akamai.steamstatic.com/steamcommunity/public/images/clans/38198503/25733639d563297f7a04c4fd68537f5b9aba3d67.png" length="0" type="image/png" />
    </item>

获取到的数据片段混乱，混合了HTML内容与类似JSON的结构：

<?xml version="1.0"?>
<string>&lt;!DOCTYPE html&gt;
&lt;html class=&quot; responsive&quot; lang=&quot;en&quot;&gt;
&lt;head&gt;
    &lt;meta http-equiv=&quot;Content-Type&quot; content=&quot;text/html; charset=UTF-8&quot;&gt;
            &lt;meta name=&quot;viewport&quot; content=&quot;width=device-width,initial-scale=1&quot;&gt;
        &lt;meta name=&quot;theme-color&quot; content=&quot;#171a21&quot;&gt;
        &lt;title&gt;Hearts of the Dungeon List - Steam News Hub&lt;/title&gt;
    &lt;link rel=&quot;shortcut icon&quot; href=&quot;/favicon.ico&quot; type=&quot;image/x-icon&quot;&gt;

ot;:"Changelog:
[list]
[*]Arry and Miri can now gain affection.
[*]The player can now view Arry and Miri's epilogue scenes. (You will have to answer their proposal one more time.)
[*]The Arry and Miri achievements have been fixed and should unlock when you reach the epilogue.
[*]The ability management backend has been 100% REDONE, and all associated bugs should be fixed.
[*]Specifically, ability use counts and levels will no longer reset if they're no longer in a player preset.
[/list]

[h2]ACTION REQUIRED:[/h2]
If you take one thing from this update, it's that [b]Arry and Miri's[/b] conversation lines were [b]broken[/b] before this update, with all their epilogue scenes being [b]hidden[/b]. 

[b]If you've been stuck at their proposal, doing it one more time should unlock their achievements and lead you to their epilogue scenes.[/b]

Additionally, I've begun work on the logbook! It's coming along nicely.

[img]https://i.imgur.com/FBdDow9.png[/img]","commentcount":1,"tags":["mod_reviewed","ModAct_870845553_1652150701_0"],"language":0,"hidden":0,"forum_topic_id":"3274690571081137373","event_gid":"3178989079011859448","voteupcount":11,"votedowncount":0,"ban_check_result":0},"published":1,"hidden":0,"rtime32_visibility_start":0,"rtime32_visibility_end":0,"broadcaster_accountid":0,"follower_count":0,"ignore_count":0,"forum_topic_id":"3274690571081137373","rtime32_last_modified":1653189104,"news_post_gid":"0","rtime_mod_reviewed":1652150697,"featured_app_tagid":0,"referenced_appids":[],"build_id":0,"build_branch&quot

public static IEnumerator GetCoroutine(string url, Action<string> OnError, Action<string> OnSuccess)
{
    using (UnityWebRequest result = UnityWebRequest.Get(url))
    {
        yield return result.SendWebRequest();

        if (result.result == UnityWebRequest.Result.ConnectionError || result.result == UnityWebRequest.Result.ProtocolError)
        {
            OnError(result.error);
        }
        else
        {
            string rawUTF8Text = result.downloadHandler.text;

            FileStream file;
            string filePath = Application.persistentDataPath + "/xmlsave.xml";
            file = File.Create(filePath);
            
            BinaryFormatter formatter = new BinaryFormatter();
            formatter.Serialize(file, rawUTF8Text);

            file.Close();

            OnSuccess(rawUTF8Text);
        }
    }
}

1. 修复数据保存错误 #

原代码用BinaryFormatter序列化字符串到文件是错误的，BinaryFormatter用于序列化.NET对象的二进制格式，直接保存字符串应该用File.WriteAllText并指定UTF-8编码：

// 替换原保存代码
string filePath = Application.persistentDataPath + "/steam_news.xml";
File.WriteAllText(filePath, rawUTF8Text, Encoding.UTF8);

2. 强制Steam返回XML格式 #

Steam可能根据请求头返回不同内容，添加请求头明确要求XML格式：

using (UnityWebRequest result = UnityWebRequest.Get(url))
{
    // 指定接受XML类型的响应
    result.SetRequestHeader("Accept", "application/rss+xml, application/xml");
    yield return result.SendWebRequest();

    // 错误处理逻辑不变
    if (result.result != UnityWebRequest.Result.Success)
    {
        OnError(result.error);
        yield break;
    }

    string rawXML = result.downloadHandler.text;
    File.WriteAllText(Application.persistentDataPath + "/steam_news.xml", rawXML, Encoding.UTF8);
    OnSuccess(rawXML);
}

3. 解析<enclosure>标签 #

获取到正确的XML后，可用XmlDocument或XDocument解析：

用XmlDocument解析 #

public void ParseRSS(string rawXML)
{
    XmlDocument doc = new XmlDocument();
    doc.LoadXml(rawXML);

    XmlNodeList items = doc.SelectNodes("//item");
    foreach (XmlNode item in items)
    {
        string title = item.SelectSingleNode("title").InnerText;
        XmlNode enclosure = item.SelectSingleNode("enclosure");
        if (enclosure != null)
        {
            string imageUrl = enclosure.Attributes["url"].Value;
            Debug.Log($"新闻标题：{title}，封面图URL：{imageUrl}");
        }
    }
}

用LINQ to XML解析 #

public void ParseRSSWithLINQ(string rawXML)
{
    XDocument doc = XDocument.Parse(rawXML);
    foreach (var item in doc.Descendants("item"))
    {
        string title = item.Element("title").Value;
        XElement enclosure = item.Element("enclosure");
        if (enclosure != null)
        {
            string imageUrl = enclosure.Attribute("url").Value;
            Debug.Log($"新闻标题：{title}，封面图URL：{imageUrl}");
        }
    }
}

4. 还原转义字符 #

如果需要处理description中的转义HTML字符（如<对应<），可使用HttpUtility.HtmlDecode：

using System.Web; // Unity中需引用System.Web.dll

string encodedDesc = item.SelectSingleNode("description").InnerText;
string decodedDesc = HttpUtility.HtmlDecode(encodedDesc);

内容的提问来源于stack exchange，提问作者Katerlad