如何通过 class 属性解析重复的 HTML 元素？

Question

我正在尝试解析具有基本相同标签的 HTML 文件。

我想要得到这个输出：

BTC - Bitcoin, BEP20(BSC), Bitcoin(Segwit)

ETH - ERC20, BEP20(BSC), POLYGON, ARBITRUM, AURORA, MATISEVM

USDT - OMNI,TRC20,ERC20,BEP20(BSC),HECO,POLYGON,FTM, AVAX-C ,ARBITRUM,METISEVM

QASH - ERC20

这是 HTML 的示例：

<div data-v-326d86f4="" class="table-box">
   <table data-v-326d86f4="">
      <tr data-v-326d86f4="">
         <td data-v-326d86f4="">BTC</td>
         <td data-v-326d86f4="" class="block-chain">
            <div data-v-326d86f4="" class="chain_box"><span data-v-326d86f4="" class="chain_name">Bitcoin</span> <span data-v-326d86f4=""><i data-v-326d86f4="" class="fa fa-caret-down"></i></span></div>
            <div data-v-326d86f4="" class="select-list"><span data-v-326d86f4="">Bitcoin</span><span data-v-326d86f4="">BEP20(BSC)</span><span data-v-326d86f4="">Bitcoin(SegWit)</span></div>
         </td>
         <td data-v-326d86f4="">0.001</td>
         <td data-v-326d86f4="">0.002</td>
      </tr>
      <tr data-v-326d86f4="">
         <td data-v-326d86f4="">ETH</td>
         <td data-v-326d86f4="" class="block-chain">
            <div data-v-326d86f4="" class="chain_box"><span data-v-326d86f4="" class="chain_name">ERC20</span> <span data-v-326d86f4=""><i data-v-326d86f4="" class="fa fa-caret-down"></i></span></div>
            <div data-v-326d86f4="" class="select-list"><span data-v-326d86f4="">ERC20</span><span data-v-326d86f4="">BEP20(BSC)</span><span data-v-326d86f4="">POLYGON</span><span data-v-326d86f4="">ARBITRUM</span><span data-v-326d86f4="">AURORA</span><span data-v-326d86f4="">METISEVM</span></div>
         </td>
         <td data-v-326d86f4="">0.012</td>
         <td data-v-326d86f4="">0.024</td>
      </tr>
      <tr data-v-326d86f4="">
         <td data-v-326d86f4="">USDT</td>
         <td data-v-326d86f4="" class="block-chain">
            <div data-v-326d86f4="" class="chain_box"><span data-v-326d86f4="" class="chain_name">OMNI</span> <span data-v-326d86f4=""><i data-v-326d86f4="" class="fa fa-caret-down"></i></span></div>
            <div data-v-326d86f4="" class="select-list"><span data-v-326d86f4="">OMNI</span><span data-v-326d86f4="">TRC20</span><span data-v-326d86f4="">ERC20</span><span data-v-326d86f4="">BEP20(BSC)</span><span data-v-326d86f4="">HECO</span><span data-v-326d86f4="">POLYGON</span><span data-v-326d86f4="">FTM</span><span data-v-326d86f4="">AVAX-C</span><span data-v-326d86f4="">ARBITRUM</span><span data-v-326d86f4="">METISEVM</span></div>
         </td>
         <td data-v-326d86f4="">30</td>
         <td data-v-326d86f4="">50</td>
      </tr>
      <tr data-v-326d86f4="">
         <td data-v-326d86f4="">QASH</td>
         <td data-v-326d86f4="" class="block-chain">
            <div data-v-326d86f4="" class="chain_box">
               <span data-v-326d86f4="" class="chain_name">ERC20</span> <!---->
            </div>
            <!---->
         </td>
         <td data-v-326d86f4="">513</td>
         <td data-v-326d86f4="">1026</td>
      </tr>
      <!-- ... -->

我正在使用 HtmlAgilityPack 库但没有成功：

Dim arqHtml As String = "C:\Users\Mattia\Desktop\ready.html"
Dim myHtml As HtmlAgilityPack.HtmlDocument = New HtmlAgilityPack.HtmlDocument()
myHtml.Load(arqHtml)
Dim myTable As HtmlAgilityPack.HtmlNode = myHtml.DocumentNode.SelectSingleNode("//table")
Dim myRows As HtmlAgilityPack.HtmlNodeCollection = myTable.SelectNodes("tr")
For Each tmpRow As HtmlAgilityPack.HtmlNode In myRows
    Dim myCells As HtmlAgilityPack.HtmlNodeCollection = tmpRow.SelectNodes("td")
    If myCells IsNot Nothing Then
        Dim myToken As String = myCells(0).InnerText
        Dim mySpans As HtmlAgilityPack.HtmlNodeCollection = myCells(1).SelectNodes("div[contains(@class,'select-list')]/span")
        If mySpans IsNot Nothing Then
            Dim myListBChain As New List(Of String)
            For Each mySpan As HtmlAgilityPack.HtmlNode In mySpans
                RichTextBox1.Text += mySpan.InnerText
            Next
            Dim allItensAsString = String.Join(", ", richtextbox1.text)
        End If
    End If
Next

这个 return 这个输出：

BitcoinBEP20(BSC)Bitcoin(SegWit)ERC20BEP20(BSC)POLYGONARBITRUMAURORAMETISEVMOMNITRC20ERC20BEP20(BSC)HECOPOLYGONFTMAVAX-CARBITRUMMETISEVMEOSBEP20(BSC)ERC20BEP20(BSC)TRC20BEP20(BSC)ZILBEP20(BSC)NEOLEGACYNEON3ERC20POLYGONERC20DAGBEP2BEP20(BSC)FTMAVAX-CERC20BEP20(BSC)ERC20BEP20(BSC)ERC20HECOBEP20(BSC)ERC20HECOERC20POLYGONERC20HECOERC20POLYGONERC20BEP20(BSC)BCHBEP20(BSC)ERC20LOOPPOLYGONBEP20(BSC)FTMAVAX-CMETISEVMERC20TOLERC20METAERC20BEP20(BSC)

如何使它成为 return 我想要的输出？

Answer 1

合并 on the original issue，在样本的最后<tr>...

<tr data-v-326d86f4="">
    <td data-v-326d86f4="">QASH</td>
    <td data-v-326d86f4="" class="block-chain">
    <div data-v-326d86f4="" class="chain_box">
        <span data-v-326d86f4="" class="chain_name">ERC20</span> <!---->
    </div>
    <!---->
    </td>
    <td data-v-326d86f4="">513</td>
    <td data-v-326d86f4="">1026</td>
</tr>

...第二个 <td> 不包含 <div class="select-list" ... >，所以...

myCells(1).SelectNodes("div[contains(@class,'select-list')]/span")

...returns Nothing，因此 NullReferenceException.

就构建您想要的输出而言，首先您需要测试是否存在这样的 <div class="select-list" ... > 元素...

If mySpans Is Nothing Then

如果没有，则保存 <div class="chain_box" ... ><span class="chain_name ... > 元素的内容...

Dim chainTextNode As HtmlAgilityPack.HtmlNode = myCells(1).SelectSingleNode(
    "div[contains(@class, 'chain_box')]/span[contains(@class, 'chain_name')]"
)

chainText = If(chainTextNode Is Nothing OrElse String.IsNullOrWhiteSpace(chainTextNode.InnerText), "(unknown)", chainTextNode.InnerText)

我添加了一些额外的处理，以防元素不存在或没有值。

如果有 <div class="select-list" ... > 元素，则保存其子 <span ... > 元素的值，用逗号分隔...

chainText = String.Join(", ", mySpans.Select(Function(span) span.InnerText))
' Alternative: chainText = String.Join(", ", From span In mySpans Select span.InnerText)

最后，创建一个新行并将其附加到您的文本框...

RichTextBox1.Text &= $"{myToken} - {chainText}{Environment.NewLine}"

完整的代码如下所示...

Dim arqHtml As String = "C:\Users\Mattia\Desktop\ready.html"
Dim myHtml As HtmlAgilityPack.HtmlDocument = New HtmlAgilityPack.HtmlDocument()
myHtml.Load(arqHtml)
Dim myTable As HtmlAgilityPack.HtmlNode = myHtml.DocumentNode.SelectSingleNode("//table")

Dim myRows As HtmlAgilityPack.HtmlNodeCollection = myTable.SelectNodes("tr")
For Each tmpRow As HtmlAgilityPack.HtmlNode In myRows
    Dim myCells As HtmlAgilityPack.HtmlNodeCollection = tmpRow.SelectNodes("td")
    If myCells IsNot Nothing Then
        Dim myToken As String = myCells(0).InnerText
        Dim mySpans As HtmlAgilityPack.HtmlNodeCollection = myCells(1).SelectNodes("div[contains(@class,'select-list')]/span")
        Dim chainText As String

        If mySpans Is Nothing Then
            Dim chainTextNode As HtmlAgilityPack.HtmlNode = myCells(1).SelectSingleNode(
                "div[contains(@class, 'chain_box')]/span[contains(@class, 'chain_name')]"
            )

            chainText = If(chainTextNode Is Nothing OrElse String.IsNullOrWhiteSpace(chainTextNode.InnerText), "(unknown)", chainTextNode.InnerText)
        Else
            chainText = String.Join(", ", mySpans.Select(Function(span) span.InnerText))
            ' Alternative: chainText = String.Join(", ", From span In mySpans Select span.InnerText)
        End If

        RichTextBox1.Text &= $"{myToken} - {chainText}{Environment.NewLine}"
    End If
Next

如果您有一个非常大的输入 HTML 文件，您可能会考虑...

将每个迭代的行附加到 StringBuilder...

outputBuilder.Append($"{myToken} - {chainText}{Environment.NewLine}")

...然后在循环后设置 RichTextBox1.Text 一次...

RichTextBox1.Text = outputBuilder.ToString()

（假设 WinForms）在循环后调用 RichTextBox1.SuspendLayout() before the loop and RichTextBox1.ResumeLayout()

...为了提高性能，但是，使用其中一种或两种方法意味着 RichTextBox1 在 HTML 完全处理之前不会显示任何输出。

如何通过 class 属性解析重复的 HTML 元素？

How can I parse repeated HTML elements by their class attribute?

html

.net

vb.net

html-parsing

html-agility-pack