HTMLAgilityPack - 你需要UseIdAttribute属性设置为true来启用此功能 [英] HTMLAgilityPack - You need to set UseIdAttribute property to true to enable this feature

问题描述

我试图用VS2008 / .NET 3.5使用HTMLAgilityPack。我得到即使我的OptionUseIdAttribute设置为true，但它应该是默认为true此错误

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.

Error Message:
 You need to set UseIdAttribute property to true to enable this feature

Stack Trace:
    at HtmlAgilityPack.HtmlDocument.GetElementbyId(String id)

我试过1.4.6版和1.4.0，既不工作。

I tried version 1.4.6 and 1.4.0, neither worked.

版本1.4.6 - Net20 / HtmlAgilityPack.dll

Version 1.4.6 - Net20/HtmlAgilityPack.dll

版本1.4.0 - Net20 / HtmlAgilityPack.dll

Version 1.4.0 - Net20/HtmlAgilityPack.dll

这是代码，

    HtmlWeb web = new HtmlWeb();
    HtmlDocument doc = web.Load(url);
    HtmlNode table = doc.GetElementbyId("tblThreads");

这也不能工作，

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

我怎样才能解决这个问题？
感谢。

How can I fix this issue? Thanks.

推荐答案

首先，我用的 ILSpy 。我导航到的HTMLDocument类，并可以看到的getElementById方法是这样的：

First I used ILSpy on the 1.4.0 HAP Dll. I navigated to the HtmlDocument class and could see that the GetElementById method looks like this:

// 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;
}

后来我ILSpy分析_nodesid，因为在你的情况下，对于一些原因，它是不被设置。 HtmlDocument.DetectEncoding（TextReader的）和HtmlDocument.Load（TextReader的）分配值_nodesid。

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".

因此，你可以尝试另一种方法来读取内容从URL借此_nodesid的价值将被明确赋值例如：

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

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");

这方法确保HtmlDocument.Load（TextReader的）之称，并在代码我可以看到_nodesid一定会得到分配，所以这种方法的可能的（我还没有编我建议代码）的工作。

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.

这篇关于HTMLAgilityPack - 你需要UseIdAttribute属性设置为true来启用此功能的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！