Simple threading problem... [Resolved]

[Cade]

This is the first day I have tried to use threads. The code below doesnt work for me. It is supposed to call TestSub every 500 ms. I created a blank windows application in VB.NET 2005 Express Edition Beta #2 and paste this directly into the code and run -

Imports System.Threading
Public Class Form1
    Dim THRD As Thread
 
    Private Shared Sub TestSub()
        MsgBox("Bleh", MsgBoxStyle.Information, "")
        Thread.Sleep(500)
    End Sub
 
    Private Sub Form1_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseDown
        THRD = New Thread(AddressOf TestSub)
        THRD.Start()
        THRD.IsBackground = True
    End Sub
 
End Class

When I click the form, it is supposed to initialize and start the thread. So I click the form... and get the messagebox, and wait a few seconds, nothing has happened. I pause the app and find out, via the intermediate window, THRD.IsAlive = False

Can anyone please tell me what is wrong with this code? I'm sure its probably some simple thing I've overlooked.

Edit: Sorry, didnt mention, I need this thread to stay alive, I'm using a loop to keep it running (with a sleep statement), but what is the proper way?

[jmcilhinney]

Well you aren't using a loop in the code you've provided. After the call to Sleep the TestSub method completes and the thread exits. Unless you raise multiple MouseDown events you're only going to get one MessageBox. You should put a Do loop inside the TestSub method if you want to continually get MessageBoxes. You should also provide a While or Until condition on that loop so that you have a way to make it exit. Also, why have you made the TestSub method Shared?

Private exitThread As Boolean
 
Private Sub TestSub
    Do
        MessageBox.Show("Test message")
        Thread.Sleep(500)
    Loop Until Me.exitThread
End Sub
 
Private Sub Form1_MouseDown(...) Handles MyBase.MouseDown
    Dim thrd As New Thread(AddressOf TestSub)
 
    Me.exitThread = False
    thrd.IsBackground = True
    thrd.Start()
End Sub

You should provide a way to set exitThread to True to terminate the thread.

[Cade]

Right, thanks
The code I use from the thread is

Private Sub CallbackRecvCheck()
        Do While sckTick.IsAlive
            Thread.Sleep(16)
 
            If sckObj.Connected <> bLastConnected Then
                If sckObj.Connected Then
                    RaiseEvent Connected()
                Else
                    RaiseEvent Disconnected()
                End If
                bLastConnected = sckObj.Connected
            End If
 
            If sckObj.Connected Then
                If sckObj.GetStream.DataAvailable Then
                    RaiseEvent RecievedDataPending()
                End If
            End If
 
        Loop
    End Sub

Loop ends automatically when thread.abort is called