This is an example of one way to parse an HTML document by using a recursive function. In this example, an html document is loaded from a text file, but the code also demonstrates (in remarks) using a web page as a source file.
When the recursive function is called, a conditional statement evaluates the html elements for child elements. If the element has children, the recursion occurs (the function calls itself) and the child of the candidate gets evaluated for children. Eventually, the function finds an element with no children, and the element's inner text, etc., is appended to a textbox. Running this program in debug mode might be helpful if my description is confusing.
import the namespaces as shown
Imports System.Windows.Forms.HtmlDocument
Imports System.Xml
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Try
Dim HTMLDocument As HtmlDocument
'Dim webclient As System.Net.WebClient = New System.Net.WebClient
'Dim url As String = "http://www.somewebsite.com"
Dim myHTML As String '= webclient.DownloadString(url)
'instead of downloading the html, lets get it from a file
Dim filePath As String = "C:\htmlsourcefile.txt"
Dim myStreamReader = New System.IO.StreamReader(filePath)
myHTML = myStreamReader.ReadToEnd
WebBrowser1.Navigate("about:blank")
Dim objectDoc = WebBrowser1.Document
WebBrowser1.Document.Write(myHTML)
WebBrowser1.ScriptErrorsSuppressed = True
HTMLDocument = WebBrowser1.Document
append("The document title is: " & HTMLDocument.Title)
Dim headElementCollection As HtmlElementCollection = _
HTMLDocument.GetElementsByTagName("head")
'call the function (no value is returned)
getChildren(headElementCollection)
append(vbCrLf)
headElementCollection = HTMLDocument.GetElementsByTagName("body")
'same function again, just for the body this time
getChildren(headElementCollection)
Catch ex As Exception
append(ex.ToString)
End Try
End Sub
This is the recursive function
Private Function getChildren(ByVal xElementCollection As HtmlElementCollection)
Dim xLabel As String
Dim parentElement As HtmlElement
For Each parentElement In xElementCollection
If parentElement.Children.Count > 0 Then
Select Case parentElement.TagName.ToLower
Case "tr" : xLabel = "Row"
Case "td" : xLabel = "Cell"
Case "th" : xLabel = "Header"
Case "a" : xLabel = "Anchor"
Case "tbody" : xLabel = "T-Body"
Case "div" : xLabel = "Division"
Case "head" : xLabel = "Head"
Case "body" : xLabel = "Body"
Case "table" : xLabel = "Table"
Case "p" : xLabel = "Paragraph"
Case Else : xLabel = "element not specified"
End Select
append("<" & xLabel & ">")
getChildren(parentElement.Children)
append("<" & xLabel & " />")
Else
If parentElement.InnerText <> "" Then
append(" " & parentElement.InnerText & "")
Else
append(" " & vbNull.ToString & "")
End If
If parentElement.GetAttribute("href").ToString <> "" Then
append(" " & parentElement.GetAttribute("href") & "")
End If
End If
Next
Return Nothing
End Function
one last thing, I prefer not to use TextBox1.append("one two three"), so I do it this way....
Private Sub append(ByVal myTextToAppend As String)
TextBox1.AppendText(myTextToAppend & vbCrLf)
Application.DoEvents()
outputXL = outputXL & myTextToAppend & vbCrLf
End Sub