[RESOLVED] problem with running duplicate threads

[dreamdelerium]

hey everyone. can anyone tell me how to call a function from a secondary thread. in my program, i have a background worker running. when the user clicks a button on the main form, i stop the background thread, run a function, but i cant get the background thread to start running again (i get an error saying the back ground worker is busy, which i dont get since i stopped the thread first. heres the code i got:

    Private Sub BackgroundWorker1_DoWork( _
        ByVal sender As Object, _
        ByVal e As System.ComponentModel.DoWorkEventArgs) _
        Handles BackgroundWorker1.DoWork

  Do Until IsItCanceled = True


            Dim worker As System.ComponentModel.BackgroundWorker
            worker = CType(sender, System.ComponentModel.BackgroundWorker)

      Dim WC As Class2 = CType(e.Argument, Class2)
            WC.FindMyPort(worker, e)

        Loop

    End Sub

    Private Sub BackgroundWorker1_ProgressChanged( _
        ByVal sender As Object, _
        ByVal e As System.ComponentModel.ProgressChangedEventArgs) _
        Handles BackgroundWorker1.ProgressChanged

        Dim state As Class2.CurrentState = _
            CType(e.UserState, Class2.CurrentState)
        Me.Label10.Text = "d"

    End Sub

Private Sub BackgroundWorker1_RunWorkerCompleted( _
    ByVal sender As Object, _
    ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs) _
    Handles BackgroundWorker1.RunWorkerCompleted

        If e.Error IsNot Nothing Then
            MsgBox("Error: " & e.Error.Message)
            BackgroundWorker1.Dispose()
        ElseIf e.Cancelled Then
            MsgBox("Word counting canceled.")
            BackgroundWorker1.Dispose()
        Else
                 BackgroundWorker1.Dispose()
        End If
    End Sub

class2:

Option Compare Text 

Imports System.Windows.Forms
Imports System.Data.OleDb
Imports System
Imports System.Data
Imports System.Data.SqlClient
Imports GsmComm.GsmCommunication
Imports GsmComm.PduConverter
Imports System.IO.Ports
Imports System.IO.Ports.SerialPort
Imports System.Text
Imports System.IO


Public Class Class2
    Public Class CurrentState
        Public LinesCounted As Integer
        Public WordsMatched As Integer
    End Class
    Public SourceFile As String
    Public CompareString As String
    Private WordCount As Integer = 0
    Private LinesCounted As Integer = 0
    Public isAmodem As Boolean = False
    Public Sub ShowMessage(ByRef MsgPDU As SmsDeliverPdu)
        Try
            Dim txtMsg As String = MsgPDU.UserDataText
            Dim FromNumber As String = MsgPDU.OriginatingAddress
            Dim FromAddress As String = MsgPDU.OriginatingAddress
            Dim TimeStamp As String = MsgPDU.GetTimestamp.ToString
            Dim MsgFromName As String = FindName(FromNumber)

            Dim AddString As String = "Insert into tblInboxMsg (MsgStatus,MsgFromNum,MsgFromName,TxtMsg,MsgTimeStamp) values" _
            & " ('New','" & FromAddress & "','" & MsgFromName & "','" & txtMsg & "','" & TimeStamp & "')"
            Debug.Print(AddString)

            '  Dim FileName As String = CurDir() & "\SMSer.mdb"
            Dim conn = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\JasonWucinski.mdb;Persist Security Info=True;Jet OLEDB:Database Password=")
            Dim Cmd As OleDbCommand
            Dim objCmd As New OleDbCommand
            Cmd = New OleDbCommand(AddString, conn)
            conn.Open()
            objCmd = New OleDbCommand(AddString, conn)
            objCmd.ExecuteNonQuery()
            conn.Close()
            'JasonWucinskiBots5
            If Not (Cmd Is Nothing) Then Cmd.Dispose()
            Cmd = Nothing
            If Not (objCmd Is Nothing) Then objCmd.Dispose()
            objCmd = Nothing
        Catch ex As Exception
            Debug.Print("ex.ToString")
            Debug.Print(ex.ToString)

        End Try
    End Sub

    Public Sub FindMyPort(ByVal worker As System.ComponentModel.BackgroundWorker, _
        ByVal e As System.ComponentModel.DoWorkEventArgs)

        If worker.CancellationPending Then
            e.Cancel = True
            Exit Sub
        Else
    
            Dim getState As Boolean = False
            Dim getManu As String
            Dim storage = getMessageStorage()
            Dim MsgLocation As Integer
            Dim counter As Integer = 0
            Try

                With comm
                    Try
                        .Open()
             
                        Dim info As IdentificationInfo = comm.IdentifyDevice
                        getManu = info.Manufacturer
                        If getManu = "huawei" Then
                        
                            Try
                            
                                Dim messages As DecodedShortMessage() = comm.ReadMessages(PhoneMessageStatus.ReceivedUnread, PhoneStorageType.Sim)
                    
                                For Each DecodedShortMessage In messages
                         
                                    MsgLocation = DecodedShortMessage.Index
                          
                                    ShowMessage(DecodedShortMessage.Data)
                  
                                    counter = counter + 1
                              Next
                            Catch ex As IOException
                             
                            End Try
                            If counter >= 1 Then
                                Try
                                  
                                 
                                    MsgBox("You got a new message")

                                Catch ex As Exception
                                  
                                End Try

                            End If
                            comm.Close()
                            Exit Try
                        End If
                    Catch Ex As IOException
              
                    Catch Ex As Exception
                        
                    End Try
                End With
            Catch ex As Exception
               
            End Try
        End If
       
        Threading.Thread.Sleep(1000)

    End Sub


End Class

when the user click a button, i run this (after a bunch of other stuff)

  Dim WC As New Class2
         IsItCanceled = False
        Me.BackgroundWorker1.RunWorkerAsync(WC)

but all i get is an error saying the thread is bussy and cant have duplicates

[MaximilianMayrhofer]

Don't loop a background worker, it's really not the way to handle this. Instead, why not have the FindMyPort method spawn itself unless it is flagged to stop? By using ThreadPool.QueueUserWorkItem() rather than simply calling the method directly each time, we can avoid memory leaks.

Public Class Class2
    Public continue As Boolean = True
 
    Public Sub FindMyPort()
        'Find your port
 
        If continue Then _
            ThreadPool.QueueUserWorkItem(AddressOf FindMyPort)
    End Sub
End Class
 
Public Class Class1
    Private WC As Class2
    
    Private Sub Class1_Load( _
        ByVal sender As System.Object, _
        ByVal e As System.EventArgs) Handles MyBase.Load
        
        WC = New Class2
        ThreadPool.QueueUserWorkItem(AddressOf WC.FindMyPort)
    End Sub
 
    Private Sub btnCancel_Click( _
        ByVal sender As System.Object, _
        ByVal e As System.EventArgs) Handles btnCancel.Click
        
        WC.continue = False
    End Sub
End Class

[dreamdelerium]

thanks for your reply. ive been trying to get your suggestion working. the only problem is that when i use this:

ThreadPool.QueueUserWorkItem(AddressOf WC.FindMyPort)

if get a blue squiggly line uner WC.FindMyPort and the error is:
Method 'Public sub FindMyPort(...)' does not have a signature compatible with delegate 'Delegate sub waitcallback(State as Object)'

what does this mean? and how do i fix it?

thanks
jason

[jmcilhinney]

When you call QueueUserWorkItem you have to pass a WaitCallback delegate. A delegate is an object with a reference to a method. AddressOf is creating a reference to your FindMyPort method. The thing is, the method must have the same signature as the delegate, i.e. the same number, type and order of parameters and the same return type. As the error message is telling you, the WaitCallback delegate is a Sub, i.e. doesn't return anything, and has a single parameter of type Object. That means that your FindMyPort method must also be a Sub and must also have one parameter of type Object. There's no necessity to actually use the parameter value in the method but it's there so that you can pass data into the method like this:

ThreadPool.QueueUserWorkItem(AddressOf WC.FindMyPort, state)

That second argument is the value that you get back from the parameter in the method.

[dreamdelerium]

ok, to fix this (i think), i changed:

    Public Sub FindMyPort(ByVal worker As System.ComponentModel.BackgroundWorker, _
        ByVal e As System.ComponentModel.DoWorkEventArgs)
'...do stuff
end sub

to this:

    Public Sub FindMyPort()
'...do stuff
end sub

this seems to work. will removing the parameters cause problems later on?

[jmcilhinney]

Why were those parameters in there in the first place? because you needed to pass data from the BackgroundWorker's DoWork event handler. Given that you're not using a BackgroundWorker anymore...

[dreamdelerium]

good point
thanks all
untill my next thread question lol