Question

HTML DOM in VB.Net

Asked by: dbnewbie

Given a URI, I need to be able to traverse the HTML DOM, and based on its contents, return a general description of the web page as an enumerated type.

How do I get the HTML DOM in VB.Net? I could use the web browser control, Navigate to the URI, then use the Document property to instantiate am HTMLDocument object. The problem is that the Document property cannot be used until Navigated event is triggered. This means either:

1. I create an event handler for Navigated. However, that would put control to that event handler. The method that called Navigate is the one that needs the HTML DOM. How can the calling method get the HTML DOM from the event handler?

2. I can Navigate to the URI, then do a while loop until the web browser object's ReadyState property is "Loaded" (or "Complete"). This approach seems to do no good as it just seems to loop infinitely. Plus, it seems very un-event driven programming to me.

Lastly, is the web browser control the only way I can get the HTML DOM?

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Asked On
2008-08-19 at 03:04:16ID23658970
Tags

.Net, Vb.Net

Topics

Microsoft Visual Basic.Net

,

.NET Framework 3.x versions

,

.NET

Participating Experts
1
Points
0
Comments
4

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Answers

 

by: rachitkohliPosted on 2008-08-19 at 03:23:13ID: 22258437

You can use the HTML object library. Add a reference to MSHTML.TLB file.

Then you can access various html objects such as Table, Row, Cell, etc.. A sample example of this could be :

Dim tb As HTMLTable '
Dim ht As New HTMLDocument
Dim htNew As HTMLDocument
Dim td As HTMLTableRow
Dim tc As HTMLTableCell
Dim strData As String

Set htNew = ht.createDocumentFromUrl("http://www.YourSite.com/", "null")

While htNew.readyState <> "complete"
    DoEvents
Wend

Set tb = htNew.getElementById("ELEMENT_ID")

For Each td In tb.rows
    For Each tc In td.cells
        strData = strData & "====" & tc.innerText
    Next
    Debug.Print strData
    strData = ""
   
Next

 

by: dbnewbiePosted on 2008-08-19 at 06:42:24ID: 22259638

This is not managed, is it?

 

by: dbnewbiePosted on 2008-08-19 at 11:55:43ID: 22262666

Here's what I have:

        Dim MyWebBrowser As New WebBrowser
        MyWebBrowser.Navigate("http://www.msn.com/") ' Apparently, this does nothing
 
        ' Loops infinitely
        While MyWebBrowser.ReadyState <> WebBrowserReadyState.Complete
        End While
 
        ' Ultimately, this is what I really need
        Dim MyHtmlDocument As HtmlDocument = MyWebBrowser.Document

                                              
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by: dbnewbiePosted on 2008-08-19 at 13:15:47ID: 22263473

Doh! This needs to be put inside the While loop:

Application.DoEvents()

20120131-EE-VQP-002

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