Vb.net WebBrowser在后续使用中失败？WebBrowser1\u文档已完成但不工作

一个VB.Net windows窗体，使用WebBrowser和HTMLDocument、HTMLTable、HTMLTableRow检索HTML表格行、列的内部文本。它只在第一次工作，但在随后的时间失败

    Private Sub WebBrowser1_DocumentCompleted(sender As Object, e As WebBrowserDocumentCompletedEventArgs) Handles WebBrowser1.DocumentCompleted
    Dim stockNo As String = ""
    Dim stockName String

    Dim doc As mshtml.HTMLDocument
    Dim table As mshtml.HTMLTable
    Dim rows As mshtml.HTMLTableRow

    doc = WebBrowser1.Document.DomDocument
    table = doc.getElementsByTagName("TABLE").item(0)
    For r = 3 To table.rows.length - 1
        rows = table.rows.item(r)

        Try
            stockNo = Replace(rows.cells(0).innerText, " ", "")
            stockName = Replace(rows.cells(1).innerText, " ", "")

        Catch ex As Exception
            Console.WriteLine("Error here: =====> " & ex.ToString)
            Console.WriteLine(rows.cells(0))              
        End Try
    Next r
End Sub    

下面是在上执行时的错误 rows.cells0.innerText

Error here: =====> System.NotSupportedException: 發生例外狀況於 HRESULT: 0x800A01B6 
Microsoft.VisualBasic.CompilerServices.LateBinding.LateGet(Object o, Type objType, String name, Object[] args, String[] paramnames, Boolean[] CopyBack)    
Microsoft.VisualBasic.CompilerServices.NewLateBinding.LateGet(Object Instance, Type Type, String MemberName, Object[] Arguments, String[] ArgumentNames, Type[] TypeArguments, Boolean[] CopyBack)    

也可以尝试WebBrowser1_ProgressChanged，但仍然不起作用。

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任何线索都有帮助。谢谢。

使用界面和对象执行相同任务的两个示例

在处理事件时，我们首先检查它的属性。如果不是，则当前文档仍然没有准备好进行解析。请注意，每个HTML页面框架可以有多个HtmlDocument，iFrame可以有其个人文档，因此此事件可以在每页引发多次

WebBrowser1.ReadyState <> WebBrowserReadyState.Complete

正如您在两个代码段中所看到的，在使用任何一个对象时，差异几乎不存在（在本例中）：

使用mshtml.HTMLDocument：

最后，在我看来，确保所有的强制转换和转换都是显式完成的。吉姆西林尼说的没错

rows.cells(0).innerText    ===> Will fail on the subsequent use but do not know why the first time is OK

rows = table.rows.item(r)  ====> OK, if all casts and conversions are done explicitly
cell0 = rows.cells.item(0)

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感谢…

错误消息与后期绑定有关，因此首先要打开Option Strict，并确保所有强制转换和转换都显式完成。如果仍然存在错误，您将获得更明确的信息。顺便说一句，您并不需要mshtml.HTMLDocument来完成此操作。您可以直接使用WebBrowser.Document更改单元格的内部文本。

Private Sub WebBrowser1_DocumentCompleted(sender As Object, e As WebBrowserDocumentCompletedEventArgs) Handles WebBrowser1.DocumentCompleted

    If WebBrowser1.ReadyState <> WebBrowserReadyState.Complete Then Return
    Dim startingRow As Integer = 3

    Dim wbDoc As HtmlDocument = DirectCast(sender, WebBrowser).Document
    Dim htmlDoc As mshtml.HTMLDocument = DirectCast(wbDoc.DomDocument, mshtml.HTMLDocument)

    Dim firstTable As mshtml.HTMLTable = htmlDoc.getElementsByTagName("TABLE").OfType(Of mshtml.HTMLTable)().FirstOrDefault()

    If firstTable IsNot Nothing Then
        For tableRow As Integer = startingRow To firstTable.rows.length - 1
            Dim row As mshtml.HTMLTableRow = DirectCast(firstTable.rows.item(tableRow), mshtml.HTMLTableRow)
            For col As Integer = 0 To 1
                Dim rowCell = DirectCast(row.cells.item(col), mshtml.HTMLTableCell)
                If rowCell IsNot Nothing Then
                    rowCell.innerText = rowCell.innerText?.Replace(" ", "")
                Else
                    'Decide what to do if the cell content is null
                End If
            Next
        Next
    End If
End Sub

Private Sub WebBrowser1_DocumentCompleted(sender As Object, e As WebBrowserDocumentCompletedEventArgs) Handles WebBrowser1.DocumentCompleted

    If WebBrowser1.ReadyState <> WebBrowserReadyState.Complete Then Return
    Dim startingRow As Integer = 3

    Dim doc As HtmlDocument = DirectCast(sender, WebBrowser).Document
    Dim firstTable As HtmlElement = doc.GetElementsByTagName("TABLE").OfType(Of HtmlElement)().FirstOrDefault()

    If firstTable?.Children.Count > 0 Then
        For tableRow As Integer = startingRow To firstTable.Children.Count - 1
            Dim rowCells As HtmlElementCollection = firstTable.Children(tableRow).Children

            If rowCells Is Nothing Then Continue For
            For col As Integer = 0 To 1
                If Not String.IsNullOrEmpty(rowCells(col).InnerText) Then
                    rowCells(col).InnerText = rowCells(col).InnerText.Replace(" ", "")
                Else
                    'Decide what to do if the cell content is null
                End If
            Next
        Next
    End If
End Sub

rows.cells(0).innerText    ===> Will fail on the subsequent use but do not know why the first time is OK

rows = table.rows.item(r)  ====> OK, if all casts and conversions are done explicitly
cell0 = rows.cells.item(0)