[RESOLVED] collections being modified-multithreading

[cengineer]

I realize this has been covered a million times before but with threading sometimes a problem is app specific. I have a multithreaded app that assigns a url to a thread which it then fetches and crawls. Now the function where I collect each threads items I have added synclocks assuming this would avoid alterations. But I get the "collection was modified, enumeration operation may not execute" error.
Please look at my code:

 For Each landingPage As String In landingPages
                        'logger.constructLog("Working on landingPage link: " & landingPage & " at " & DateTime.Now.ToString, True)
                        Dim thread = New Thread(AddressOf processQuery)
                        count = count + 1
                        thread.Name = "Worm" & count
                        thread.Start(landingPage)
                        ThreadList.Add(thread)
                        If numThread >= 10 Then
                            Exit For
                        Else
                            numThread = numThread + 1
                        End If
                        'processQuery(landingPage)
                        logger.constructLog("Complete with link search: " & landingPage & " at " & DateTime.Now.ToString, True)
                    Next
...process function


If Not String.IsNullOrEmpty(html) Then
                If searchChoice = "something1" Or fromUrl.Contains("something1") Then
                    SyncLock something1lock
                        links = parsingUtilities.Getsomething1LinksFromHtml(fromUrl, html, searchItem)
                        posts = parsingUtilities.GetPsomething1FromHtml(links)
                    End SyncLock
                ElseIf searchChoice = "something2" Or fromUrl.Contains("something2") Then
                    SyncLock something2lock
                        links = parsingUtilities.Getsomething2LinksFromHtml(fromUrl, html, searchItem)
                        posts = parsingUtilities.GetPsomething2FromHtml(links)
                    End SyncLock
                ElseIf searchChoice = "something3" Or fromUrl.Contains("something3") Then
                    SyncLock something3lock
                        links = parsingUtilities.Getsomething3LinksFromHtml(fromUrl, html, searchItem)
                        posts = parsingUtilities.GetPsomething3FromHtml(links)
                    End SyncLock
                ElseIf searchChoice = "something4" Or fromUrl.Contains("something4") Then
                    SyncLock something4lock
                        links = parsingUtilities.GetsomethingLinksFromHtml(fromUrl, html, searchItem)
                        posts = parsingUtilities.GetPsomething4FromHtml(links)
                    End SyncLock
                End If


                Dim ExecutionError As String
                Try
                    SyncLock dlock

                        For Each l As String In links
                            finallinks.Add(l)
                        Next
                        For Each p As String In posts
                            finalposts.Add(p)
                        Next

                    End SyncLock

                Catch ex As ApplicationException
                    messagebox.show(ex.message.tostring)


                End Try


               
                Try
                    SyncLock dlock

                        Dim filepath As String = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments)

                        Dim outfile As New StreamWriter(filepath & "\Visual Studio 2008\Projects\output.txt", True)



                        Dim i As Integer = 0


                        For Each link As String In finallinks

                            While i < posts.Count()
                                postlink = finalposts.Item(i)
                                i = i + 1

' ...the rest is code to enter data into a database

Also I forgot to mention that this entire process that includes the creation of threads for the url fetching is being run by a background thread also. I needed an individual thread to run this processes since the main thread needs to handle something else.
I thought I would post the part where I create the threads and assign them since I think there is an issue here as well, I




I know the code is poorly done...so please offer suggestions.
Thanks