如何通过类属性解析重复的HTML元素？

Question

我试图用基本相同的标记来解析HTML文件。

我想得到这个输出：

BTC -比特币，BEP20，比特币

ERC20，BEP20，多边形，ARBITRUM，AURORA，MATISEVM

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

卡什- ERC20

下面是HTML的一个示例：

<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

这将返回以下输出：

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)

如何使它返回我想要的输出？

Answer 1

结合my comment on the original issue，在样本中的最后一个<tr>中.

<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>

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

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

...returns Nothing，也就是NullReferenceException。

就构建所需的输出而言，首先需要测试这样的<div class="select-list" ... >元素是否存在.

If mySpans Is Nothing Then

如果没有，那么保存<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)

我增加了一些额外的处理，以防该元素不存在或没有值。

如果有一个<div class="select-list" ... >元素，那么保存它的子<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，构建并在文本框中添加一个新行.

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

完整的代码看起来像这样..。

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}")

...and然后在循环之后设置RichTextBox1.Text一次..。RichTextBox1.Text = outputBuilder.ToString()

• (假设WinForms)在循环之前调用RichTextBox1.SuspendLayout()，在循环

之后调用RichTextBox1.ResumeLayout()

但是，...to可以提高性能，但是，使用这两种方法都意味着RichTextBox1在完全处理HTML之前不会显示任何输出。