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vb.net 2008 html parsing and listbox

Im fairly new to programming, but what I want my program to do is to visit a webpage that has a bunch of links on the page containing usernames, then pull the user names from the page and add them to a list box
Heres a sample of the html

<table style="margin-left:auto;margin-right:auto;"><tr><td style="font-size:8pt;text-align:center;" class="color">
<div><b><a href="http://www.website.com/username1">
chronic</a>
</b></div>

<a href="http://www.website.com/username1">
    <img class="pic1" onmouseover="showInfo5('chronic', '', '');this.className='pic2';" onmouseout="this.className='pic1';return nd();" src="http://www.website.com/file/pic/user/chronic_75.jpg" alt="" height="75" width="56" />
</a>
</td>

</tr>
</table></td>
<td style="text-align:center;vertical-align;middle;">
<table style="margin-left:auto;margin-right:auto;"><tr><td style="font-size:8pt;text-align:center;" class="color">
<div><b><a href="http://www.website.com/username2">
dantheman2108</a>
</b></div>

I would like for it to pull the data after <a href="http://www.website.com/ and put the username into a listbox, any ideas or suggestions on how i would go about this, ive been using the web browser control

0
j0eh4x
Asked:
j0eh4x
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1 Solution
 
oobaylyCommented:
Use the HttpWebRequest class to get the html on the page, then use a RegEx to extract the usernames
    Dim re As New Regex("<a href""http://www.website.com/(<?Username>/+?)""")
    Dim usernames As New List(Of String)()
    For Each m As Match In re.Matches(htmlText)
      usernames.Add(m.Groups("Username"))
    Next

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0
 
j0eh4xAuthor Commented:
having trouble with this code


under For it has "statement can not appear outside of a method body"
and under usernames, it says "declaration expected"

  Dim re As New Regex("<a href""http://www.website.com/(<?Usernamer/+?)""")
    For Each m As Match In re.Matches(htmlText)
      usernames.Add(m.Groups("Username"))
    Next

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0
 
oobaylyCommented:
As the compile error suggests, you need to place the for loop in a method or event handler. Also, you haven't declared the List to be populated. Finally, you misspelt Username in the Regex
Private Function PopulateUsernames(htmlText As String) As List(Of String)
  Dim re As New Regex("<a href""http://www.website.com/(<?Username>/+?)""")
  Dim usernames As New List(Of String)()
  For Each m As Match In re.Matches(htmlText)
    usernames.Add(m.Groups("Username"))
  Next
  Return usernames;
End Sub

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j0eh4xAuthor Commented:
m.Groups("Username")   "Value of type 'system.text.regularexpressions.group' cannot be converted to string'.
Imports System.net
Imports System.Text.RegularExpressions
 
Public Class Form1
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim myReq As HttpWebRequest = _
         WebRequest.Create("http://www.website.com/")
    End Sub
    Private Function PopulateUsernames(ByVal htmlText As String) As List(Of String)
        Dim re As New Regex("<a href""http://www.website.com/(<?Username>/+?)""")
        Dim usernames As New List(Of String)()
        For Each m As Match In re.Matches(htmlText)
            usernames.Add(m.Groups("Username"))
        Next
        Return usernames
    End Function
End Class

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0
 
oobaylyCommented:
Sorry about that last error, forgot that it should use the Value property of the match:

usernames.Add(m.Groups("Username").Value)

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0
 
j0eh4xAuthor Commented:
how would i add it to the listbox
0
 
oobaylyCommented:
Assuming your listbox is called listBox1:
'' Inside the Loop
listBox1.Items.Add(m.Groups("Username").Value)

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0
 
j0eh4xAuthor Commented:
oobayly i greatly appreciate your help, i have one last dumb question
attached is the final program, on previous programs ive put my code in buttons. how do i trigger this Private Function PopulateUsernames
Imports System.Net
Imports System.Text.RegularExpressions
 
Public Class Form1
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim myReq As HttpWebRequest = _
         WebRequest.Create("http://www.website.com/browse/")
    End Sub
    Private Function PopulateUsernames(ByVal htmlText As String) As List(Of String)
        Dim re As New Regex("<a href""http://www.website.com/(<?Username>/+?)""")
        Dim usernames As New List(Of String)()
        For Each m As Match In re.Matches(htmlText)
            usernames.Add(m.Groups("Username").Value)
            '' Inside the Loop
            ListBox.Items.Add(m.Groups("Username").Value)
        Next
        Return usernames
 
    End Function
End Class

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0
 
oobaylyCommented:
Instead of using HttpWebRequest, use the WebClient, download the html as a string, and pass it to PopulateUsernames. The 3 lines below should go in the Load event
Dim client As New WebClient()
Dim htmlText As String = client.DownloadString("http://www.website.com/")
PopulateUsernames(htmlText)

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0
 
j0eh4xAuthor Commented:
i tried the following code but got nothing in the list box

Imports System.Net
Imports System.Text.RegularExpressions
 
Public Class Form1
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim client As New WebClient()
        Dim htmlText As String = client.DownloadString("http://www.stlpunk.com/browse")
        PopulateUsernames(htmlText)
    End Sub
    Private Function PopulateUsernames(ByVal htmlText As String) As List(Of String)
        Dim re As New Regex("<a href""http://www.stlpunk.com/(<?Username>/+?)""")
        Dim usernames As New List(Of String)()
        For Each m As Match In re.Matches(htmlText)
            usernames.Add(m.Groups("Username").Value)
            '' Inside the Loop
            ListBox.Items.Add(m.Groups("Username").Value)
        Next
        Return usernames
 
    End Function
 
End Class

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oobaylyCommented:
There's nothing obviously wrong with the code, so all I can suggest is adding some breakpoints and verifying that the HTML returned is valid and that some matches are being returned.
0
 
j0eh4xAuthor Commented:
i used to following code to put a break in time after receiving the html then i set a textbox equal to the htmltext variable to make sure its recieving the html ok.... still not populating the list box though

Imports System.Net
Imports System.Text.RegularExpressions
 
Public Class Form1
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim client As New WebClient()
        Dim htmlText As String = client.DownloadString("http://www.stlpunk.com/browse/mode_recent/")
        Dim timeOut As DateTime = Now.AddMilliseconds(5000)'pause for 5 seconds
        Do
            Application.DoEvents()
        Loop Until Now > timeOut
        TextBox1.Text = htmlText ' display html
        PopulateUsernames(htmlText)
 
 
    End Sub
    Private Function PopulateUsernames(ByVal htmlText As String) As List(Of String)
        Dim re As New Regex("<a href""http://www.stlpunk.com/(<?Username>/+?)""")
        Dim usernames As New List(Of String)()
        For Each m As Match In re.Matches(htmlText)
            usernames.Add(m.Groups("Username").Value)
            '' Inside the Loop
            ListBox.Items.Add(m.Groups("Username").Value)
        Next
        Return usernames
 
    End Function
 
End Class

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oobaylyCommented:
By breakpoint I mean a debugging breakpoint, so that you can inspect the code returned by the WebClient.
You don't need to block the Load event using the loop as DownloadString will block until it returns a string (or throws an exception).

http://msdn.microsoft.com/en-us/library/ktf38f66(VS.71).aspx
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