blocks|key|2559847|text|首先，我在1.4.0HAPDLL上使用了ILSpy。我导航到HtmlDocument类，可以看到GetElementById方法如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|2559848|//+HtmlAgilityPack.HtmlDocument
///+<summary>
///+Gets+the+HTML+node+with+the+specified+'id'+attribute+value.
///+</summary>
///+<param+name="id">The+attribute+id+to+match.+May+not+be+null.</param>
///+<returns>The+HTML+node+with+the+matching+id+or+null+if+not+found.</returns>
public+HtmlNode+GetElementbyId(string+id)
{
++++if+(id+==+null)
++++{
++++++++throw+new+ArgumentNullException("id");
++++}
++++if+(this._nodesid+==+null)
++++{
++++++++throw+new+Exception(HtmlDocument.HtmlExceptionUseIdAttributeFalse);
++++}
++++return+this._nodesid[id.ToLower()]+as+HtmlNode;
}|code-block|syntax|javascript|2559849|然后，我让ILSpy来分析"_nodesid"，因为在您的例子中，由于某种原因，它没有被设置。"HtmlDocument.DetectEncoding(TextReader)“和"HtmlDocument.Load(TextReader)”为"_nodesid“赋值。|2559850|因此，您可以尝试另一种方法从URL读取内容，从而明确地分配"_nodesid“值。|2559851|var+doc+=+new+HtmlDocument();
var+request+=+(HttpWebRequest)WebRequest.Create(url);
request.Method+=+"GET";
using+(var+response+=+(HttpWebResponse)request.GetResponse())
{
++++using+(var+stream+=+response.GetResponseStream())
++++{
++++++++doc.Load(stream);
++++}
}
var+table+=+doc.GetElementbyId("tblThreads");|2559852|这种方法确保调用"HtmlDocument.Load(TextReader)“，在该代码中，我可以看到_nodesid肯定会得到分配，因此这种方法可能(我还没有编译我建议的代码)可以工作。|2559853|entityMap|0|LINK|mutability|MUTABLE|url|http://ilspy.net/^0|K|5|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@$A|Z|B|10|1|11]]|C|$]]|$1|D|3|E|5|F|7|12|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|13|8|@]|9|@]|C|$]]|$1|K|3|L|5|6|7|14|8|@]|9|@]|C|$]]|$1|M|3|N|5|F|7|15|8|@]|9|@]|C|$G|H]]|$1|O|3|P|5|6|7|16|8|@]|9|@]|C|$]]|$1|Q|3|-4|5|6|7|17|8|@]|9|@]|C|$]]]|R|$S|$5|T|U|V|C|$W|X]]]]

First I used <a href="http://ilspy.net/" rel="nofollow">ILSpy</a> on the 1.4.0 HAP Dll. I navigated to the HtmlDocument class and could see that the GetElementById method looks like this:

<pre><code>// HtmlAgilityPack.HtmlDocument
/// &lt;summary&gt;
/// Gets the HTML node with the specified 'id' attribute value.
/// &lt;/summary&gt;
/// &lt;param name="id"&gt;The attribute id to match. May not be null.&lt;/param&gt;
/// &lt;returns&gt;The HTML node with the matching id or null if not found.&lt;/returns&gt;
public HtmlNode GetElementbyId(string id)
{
 if (id == null)
 {
 throw new ArgumentNullException("id");
 }
 if (this._nodesid == null)
 {
 throw new Exception(HtmlDocument.HtmlExceptionUseIdAttributeFalse);
 }
 return this._nodesid[id.ToLower()] as HtmlNode;
}
</code></pre>

I then got ILSpy to analyze "_nodesid", because in your case for some reason it is not being set. "HtmlDocument.DetectEncoding(TextReader)" and "HtmlDocument.Load(TextReader)" assigns value to "_nodesid".

Hence you could try an alternative method to read the content from the URL whereby the "_nodesid" value will be definitely assigned e.g.

<pre><code>var doc = new HtmlDocument();
var request = (HttpWebRequest)WebRequest.Create(url);
request.Method = "GET";
using (var response = (HttpWebResponse)request.GetResponse())
{
 using (var stream = response.GetResponseStream())
 {
 doc.Load(stream);
 }
}
var table = doc.GetElementbyId("tblThreads");
</code></pre>

This approach ensures that "HtmlDocument.Load(TextReader)" is called, and in that code I can see that _nodesid will definitely get assigned, so this approach may (I haven't compiled the code I've suggested) work.

I am trying to use HTMLAgilityPack with VS2008/.Net 3.5. I get this error even if I set the OptionUseIdAttribute to true, though it is supposed to be true by default.

<pre><code>Error Message:
 You need to set UseIdAttribute property to true to enable this feature

Stack Trace:
 at HtmlAgilityPack.HtmlDocument.GetElementbyId(String id)
</code></pre>

I tried version 1.4.6 and 1.4.0, neither worked.

Version 1.4.6 - Net20/HtmlAgilityPack.dll

Version 1.4.0 - Net20/HtmlAgilityPack.dll

This is the code,

<pre><code> HtmlWeb web = new HtmlWeb();
 HtmlDocument doc = web.Load(url);
 HtmlNode table = doc.GetElementbyId("tblThreads");
</code></pre>

This didn't work either,

<pre><code> HtmlWeb web = new HtmlWeb();
 HtmlDocument doc = new HtmlDocument { OptionUseIdAttribute = true };
 doc = web.Load(url);
 HtmlNode table = doc.GetElementbyId("tblThreads");
</code></pre>

How can I fix this issue?
Thanks.

HTMLAgilityPack - You need to set UseIdAttribute property to true to enable this feature

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我试图在use 2008/.NET 3.5中使用HTMLAgilityPack。即使我将OptionUseIdAttribute设置为true，也会得到这个错误，尽管默认情况下它应该是true。Error Message: You need to set UseIdAttribute property to true ...

HTMLAgilityPack -您需要将UseIdAttribute属性设置为true以启用此功能-腾讯云开发者社区-腾讯云

问HTMLAgilityPack -您需要将UseIdAttribute属性设置为true以启用此功能
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