[VB6] - Module for working with multithreading.

[hennyere]

Hello The trick,

Thank you very much for your project. It's helped a lot here

Now I need an anointing to stop the threads immediately without waiting for them to finish.

I tried the code below and things seem to be working fine. Please, do you have any other suggestions?

Private Declare Function TerminateThread Lib "kernel32" (ByVal hThread As Long, ByVal dwExitCode As Long) As Long

Public Function StopThreadImmediately(ByVal lAsynchId As Long) As Long
    Dim hThread As Long
    Const THREAD_TERMINATE As Long = 1
    ' // Unsupported in IDE
    If bIsInIDE Then Exit Function
        If lAsynchId > 0 Then
            hThread = OpenThread(THREAD_TERMINATE, 0, lAsynchId)
            If Not (hThread = 0) Then
                StopThreadImmediately = TerminateThread(hThread, 0)
                CloseHandle hThread
            End If
        End If
End Function

[The trick]

Hello The trick,

Thank you very much for your project. It's helped a lot here

Now I need an anointing to stop the threads immediately without waiting for them to finish.

I tried the code below and things seem to be working fine. Please, do you have any other suggestions?

Private Declare Function TerminateThread Lib "kernel32" (ByVal hThread As Long, ByVal dwExitCode As Long) As Long

Public Function StopThreadImmediately(ByVal lAsynchId As Long) As Long
    Dim hThread As Long
    Const THREAD_TERMINATE As Long = 1
    ' // Unsupported in IDE
    If bIsInIDE Then Exit Function
        If lAsynchId > 0 Then
            hThread = OpenThread(THREAD_TERMINATE, 0, lAsynchId)
            If Not (hThread = 0) Then
                StopThreadImmediately = TerminateThread(hThread, 0)
                CloseHandle hThread
            End If
        End If
End Function

It's the bad practice to use TerminateThread because there is no resource releasing in this case. It's better to notify a thread (for example PostMessage/PostThreadMessage in certain cases) you want to finish it. If your thread is in waiting state you can use alertable state and notify by posting an APC request.

[hennyere]

It's the bad practice to use TerminateThread because there is no resource releasing in this case. It's better to notify a thread (for example PostMessage/PostThreadMessage in certain cases) you want to finish it. If your thread is in waiting state you can use alertable state and notify by posting an APC request.

Hi The Trick,

I'm glad to see you here while I'm having a coffee.

Thanks for letting me know about using TerminateThread.

I'm trying to adapt your module into a project, and I would like to ask a question:

In a very simple approach, we have some sql statements that need to be executed asynchronously. Please keep in mind that this is a summary code, therefore the RunSqlAssync function is called in several places in the project.

Form1.frm

Private Sub Form_Load()
    modMultiThreading.Initialize
    modMultiThreading.EnablePrivateMarshaling True
End Sub

Private Sub Form_Unload(Cancel As Integer)
    modMultiThreading.Uninitialize
End Sub

Private Sub Command1_Click()
    RunSqlAssync "UPDATE mytable SET myfield1=100 WHERE myfield1=1000;"
    RunSqlAssync "UPDATE mytable SET myfield1=200 WHERE myfield1=2000;"
End Sub

Module1.bas

Public Sub RunSqlAssync(ByVal xSql As String) 
    Dim zTObj As Object, zTAsynchID As Long
    Set zTObj = modMultiThreading.CreatePrivateObjectByNameInNewThread("VBThreadClass", , zTAsynchID)
    modMultiThreading.AsynchDispMethodCall zTAsynchID, "RunSqlEx", VbMethod, Nothing, "", xSql
End Function

VBThreadClass.cls

Public Sub RunSqlEx(ByVal xSql As String)
    Dim xCmd As Object
    Set xCmd = CreateObject("ADODB.Command")
    xCmd.ActiveConnection = Db
    xCmd.CommandType = adCmdText
    xCmd.CommandText = xSql
    xCmd.Execute , , adExecuteNoRecords
    Set xCmd = Nothing
End Sub

As you noticed, every time I call RunSqlAssync, this Sub asynchronously executes RunSqlEx. This seems to work fine, but I have 2 questions:

1. What happens to the Thread when RunSqlEx reaches the end? Is it simply finished?
2. How many Threads can be executed in parallel?

I've been working with C# for years and don't have much experience with Vb6.

[The trick]

1. What happens to the Thread when RunSqlEx reaches the end? Is it simply finished?
2. How many Threads can be executed in parallel?.

1. Yes. ActiveXThreadProc keeps track of object reference. When it reaches 1 (no external thread use reference) it ends.
2. It depends on system resources.