DataSet with ThreadPool causing problems...

[Lanibox]

Hey, im allready getting bit fustrated with this. Been trying to find solution for few hours allready.

So, im making proxy scraper and beacause adding proxies directly to datagridview was causing program to run slow, somebody said I should use database for it.

As I said on thread title, this is using ThreadPool and its giving me this error.

DataTable internal index is corrupted: 5

So, this is my code that should add proxy:

                Dim proxyregex As New Regex("[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}:[0-9]{1,4}")
                Dim proxies As MatchCollection = proxyregex.Matches(html)
                Dim pcount As Integer = 0

                For Each m As Match In proxies
                    Dim splitted() As String = m.Value.Split(":"c)
                    If splitted.Length > 1 Then
                        Dim newProxyRow As DataRow = ProxiesDBDataSet.Tables(0).NewRow()
                        newProxyRow(0) = tcount.ToString
                        newProxyRow(1) = splitted(0).ToString
                        newProxyRow(2) = splitted(1).ToString
                        ProxiesDBDataSet.Tables(0).Rows.Add(newProxyRow)
                        tcount += 1
                        pcount += 1
                    End If
                Next

Any help?

[jmcilhinney]

Is your DataTable bound to a DataGridView at the time? If so then that may be the root of the issue.

By the way, why are you using the ThreadPool? That is generally for queuing multiple work items. If all you want to do is run a single loop on a single thread then there are better options.

[Niya]

Hmm....We need a little more info on what you're doing. As suggested by jmc, it would help to know if that DataTable is bound or not. Also, I'd like to know what it is you're doing that requires threading and more specifically, how you're doing it. Also, explain what this 'proxy' thing is about because that totally lost me

Your error instinctively tells me a couple of SyncLocks may need to be factored in to your code but I can't make such an assertion accurately without knowing exactly what you're doing.

[Baselx]

Thank you

[Lanibox]

Is your DataTable bound to a DataGridView at the time? If so then that may be the root of the issue.

By the way, why are you using the ThreadPool? That is generally for queuing multiple work items. If all you want to do is run a single loop on a single thread then there are better options.

Hmm....We need a little more info on what you're doing. As suggested by jmc, it would help to know if that DataTable is bound or not. Also, I'd like to know what it is you're doing that requires threading and more specifically, how you're doing it. Also, explain what this 'proxy' thing is about because that totally lost me

Your error instinctively tells me a couple of SyncLocks may need to be factored in to your code but I can't make such an assertion accurately without knowing exactly what you're doing.

I use threadpool beacause there is over few hundred sites where my programs scrapes proxies.
And yes, its bound to datagridview.

This is how I have made it now:

    Public Sub dowork()
        For i = 0 To ProxiesDBDataSet.Proxies.Rows.Count - 1
            ProxiesDBDataSet.Proxies.Rows(i).Delete()
        Next
        Dim upperbound As Integer = multisource.Items.Count() - 1
        totalTaskCount = upperbound
        For i = 0 To upperbound
            ThreadPool.QueueUserWorkItem(AddressOf Scrape, multisource.Items(i).ToString())
        Next
    End Sub

    Private Sub Scrape(ByVal webaddress As Object)
        Dim website As String = CType(webAddress, String)
        Dim http As New Chilkat.Http()
        Dim success As Boolean = http.UnlockComponent(ChilKatLicenses.Lic_Chilkat_HTTP)
        If success = True Then
            http.ConnectTimeout = 5
            Dim html As String = http.QuickGetStr(website)
            If String.IsNullOrEmpty(html) Then
                logger("Timedout: " & website)
            Else
                Dim proxyregex As New Regex("[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}:[0-9]{1,4}")
                Dim proxies As MatchCollection = proxyregex.Matches(html)
                Dim pcount As Integer = 0

                For Each m As Match In proxies
                    Dim splitted() As String = m.Value.Split(":"c)
                    If splitted.Length > 1 Then
                        Dim newProxyRow As DataRow = ProxiesDBDataSet.Tables(0).NewRow()
                        newProxyRow(0) = tcount.ToString
                        newProxyRow(1) = splitted(0).ToString
                        newProxyRow(2) = splitted(1).ToString
                        ProxiesDBDataSet.Tables(0).Rows.Add(newProxyRow)
                        tcount += 1
                        pcount += 1
                    End If
                Next

                Dim msg As String = "Scraped " & pcount.ToString & " proxies from " & website
                SetControlText(totalcount, tcount.ToString)
                SetControlText(Label28, msg)
                logger(msg)
                Interlocked.Decrement(totalTaskCount)
                If Interlocked.Read(totalTaskCount) <= 0 Then
                    logger("Scraping completed for website " & website)
                End If
            End If
        End If
    End Sub

[jmcilhinney]

As I said, the fact that it's bound is probably the issue. When you make a change to the DataTable that will cause a change in the DataGridView. That means that you are updating the UI from a secondary thread, which is a no-no. You should be marshalling a method call to the UI thread to update the DataTable. From the looks of the fact that you're calling a SetControlText method you already know how to do that. I would tend to do this:

Private Sub AddRowToDataTable(table As DataTable, ParamArray values As Object())
    If InvokeRequired Then
        Invoke(New Action(Of DataTable, Object())(AddressOf AddRowToDataTable), table, values)
    Else
        table.Rows.Add(values)
    End If
End Sub

and then replace this:

                        Dim newProxyRow As DataRow = ProxiesDBDataSet.Tables(0).NewRow()
                        newProxyRow(0) = tcount.ToString
                        newProxyRow(1) = splitted(0).ToString
                        newProxyRow(2) = splitted(1).ToString
                        ProxiesDBDataSet.Tables(0).Rows.Add(newProxyRow)

with this:

AddRowToDataTable(ProxiesDBDataSet.Tables(0), tcount.ToString(), splitted(0).ToString(), splitted(1).ToString())

[Lanibox]

As I said, the fact that it's bound is probably the issue. When you make a change to the DataTable that will cause a change in the DataGridView. That means that you are updating the UI from a secondary thread, which is a no-no. You should be marshalling a method call to the UI thread to update the DataTable. From the looks of the fact that you're calling a SetControlText method you already know how to do that. I would tend to do this:

Private Sub AddRowToDataTable(table As DataTable, ParamArray values As Object())
    If InvokeRequired Then
        Invoke(New Action(Of DataTable, Object())(AddressOf AddRowToDataTable), table, values)
    Else
        table.Rows.Add(values)
    End If
End Sub

and then replace this:

                        Dim newProxyRow As DataRow = ProxiesDBDataSet.Tables(0).NewRow()
                        newProxyRow(0) = tcount.ToString
                        newProxyRow(1) = splitted(0).ToString
                        newProxyRow(2) = splitted(1).ToString
                        ProxiesDBDataSet.Tables(0).Rows.Add(newProxyRow)

with this:

AddRowToDataTable(ProxiesDBDataSet.Tables(0), tcount.ToString(), splitted(0).ToString(), splitted(1).ToString())

Thanks alot! No more that error and works very fast

Anyway, I added this into scraper

                        Dim row As ProxiesDBDataSet.ProxiesRow = ProxiesDBDataSet.Proxies.FindByIpPort(splitted(0).ToString, splitted(1).ToString)
                        If row Is Nothing Then
                            AddRowToDataTable(ProxiesDBDataSet.Tables(0), tcount.ToString(), splitted(0).ToString(), splitted(1).ToString())
                            tcount += 1
                            pcount += 1
                        End If

And it should check if table allready contains that row but it still gives this error:
Column Ip Port is constrained to be unique. Value ..... is already present.

On this code:

    Private Sub AddRowToDataTable(table As DataTable, ParamArray values As Object())
        If InvokeRequired Then
            Invoke(New Action(Of DataTable, Object())(AddressOf AddRowToDataTable), table, values)
        Else
            table.Rows.Add(values)
        End If
    End Sub

Any ideas?

[jmcilhinney]

You could call the table's Select method to see if there is an existing row with a particular value in a particular column. That will be a bit on the slow side though, so I'd suggest a different option. I'd use a HashSet to store the values that are in that column. When you want to add a new row, you add the value you want in that column to the HashSet first. If the Add method returns True then the item was added, meaning that it was not already in the HashSet, meaning that it's not already in the DataTable, so you can go ahead and add the row. If Add returns False then the value already exists so you shouldn't add the row. Note that that check can safely be performed on the background thread because it doesn't affect the DataTable so it doesn't affect the grid.

[Lanibox]

Could you give some example of this? I havent heard of this HashSet before, checked on google but cant understand how to make it work like how you said.

[jmcilhinney]

It's not rocket science. You already know how to Add an item to a collection because you're already doing it in the code you posted. In the case of a HashSet, it cannot contain duplicates so Add returns True or False depending on whether the item was unique and added successfully or a duplicate and rejected. You simply use that Boolean value to determine whether to add your row or not.