htmlagilitypack looping pages

Question

so i use for loop to change page like website/page=1, example

For i As Integer = NumericUpDown1.Value To NumericUpDown2.Value
    Pnumber = i
    Scrape()
Next

and

 Dim base As String = ComboBox1.Text & Pnumber
    Dim Webget = New HtmlWeb()
    Dim doc = Webget.Load(base)
    For Each node As HtmlNode In doc.DocumentNode.SelectNodes("//tbody//td//a[contains(@href, 'player')]")
        If Not ListBox1.Items.Contains(node.InnerHtml) Then
            ListBox1.Items.Add(node.InnerHtml)
        End If
    Next
    Label2.Text = "Count: " & ListBox1.Items.Count

first few pages work, but it throws exception, how can i change page other way idk... or wait it to finish scraping ? oh and i can use sleep but it slows down the process.

It wont help you but:

An unhandled exception of type 'System.NullReferenceException' occurred in scraper 2.exe Additional information: Object reference not set to an instance of an object.

It throws error in this line For Each node As HtmlNode In doc.DocumentNode.SelectNodes("//tbody//td//a[contains(@href, 'player')]")

I gave you the wrong dupe link. This is correct: [What is a NullReferenceException and how do I fix it?](http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it) — Bjørn-Roger Kringsjå, Jan 11 '15 at 16:04
You need to ensure that `doc`, `doc.DocumentNode` and `doc.DocumentNode.SelectNodes` is *not* null aka. nothing. — Bjørn-Roger Kringsjå, Jan 11 '15 at 16:14
For reference types ("opposite" of value types) use the **[Is operator](http://msdn.microsoft.com/en-us/library/kb136x1y.aspx)**. Example: `If (Not doc Is Nothing) Then` — Bjørn-Roger Kringsjå, Jan 11 '15 at 16:36
Great! Then I'll send you to this post: [How to update the GUI from another thread](http://stackoverflow.com/questions/661561/how-to-update-the-gui-from-another-thread-in-c) It's C# but the principal is the same for vb.net. Use `Me.Invoke(Sub() ...)`. — Bjørn-Roger Kringsjå, Jan 11 '15 at 16:45
i think for loop goes too fast to process it so throws error — newbhere, Jan 11 '15 at 16:49

htmlagilitypack looping pages

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