Ending a sub-routine/thread from an event

Ending a sub-routine/thread from an event

• SukhiNew

  The background worker uses threading. It is the recommended way to use

  threads according to the help.

  I am an amatuer programmer, so Spotty can probably explain this much better

  than I.

  (I am a DOS programmer from way back when, and am just now getting into

  Windows programming.)

  
  
  

• Biswajitghosh25

  Background worker process is a class/control which is designed to simplify the task of running a background process.

  If you comfortable using threading then I'd so go for it and continue this way.

  If you new to the idea of running a background/process and running 2005/Express then I would definately take a look at it along with the samples associated with it.

  
  

• Jimmy Gao

  I guess the general answer is you need an exit condition on you loop to allow it to exit the loop - or you kill/terminate the thread.

  So in a single thread example. You start a infinite loop and the way to stop it is to set a condition which causes the loop to exit. In this case I'm using a Public Variable on the module.

  You'd set this property in the event

  Public Class Form1
  Private Sub StartLoopProcess(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
  Mod1.i = 0
  Mod1.foo()
  End Sub

  Private Sub StopLoopProcess(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
  Mod1.i = -1
  MsgBox(Mod1.i)
  End Sub

  Private Sub ShowLoopCounter(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
  MsgBox(Mod1.i)
  End Sub
  End Class

  
  Module Mod1
  Public i As Integer = 0

  Sub foo()
  '//Cause an infinite loop in sub
  Do While True
  Application.DoEvents()

  If i = -1 Then '//Exit Condition
  Exit Do
  Else
  i = i + 1
  End If
  Loop
  End Sub
  End Module
  

  I'm not sure if this is completely applicable to you example but I wouldnt think you can say - stop this sub in this thread. I dont seem to have ever seen this in any examples.

  
  

• mortiz2112

  ^ Very interesting! Is there an advantage to using the backgroundworker vs threading (i'm pretty new to this).

  Thanks,

  Josh

  
  

• Sudhakar.hcitek

  Thanks - i should've thought of that! Works great. :)
  

• cwng

  For those who might want to use the background worker:

  Imports System

  Imports System.ComponentModel

  Imports System.Threading

  Imports System.Windows.Forms

  Public Class Form1

  Inherits Form

  Public Sub New()

  InitializeComponent()

  End Sub

  Private Sub setTextBackgroundWorkerBtn_Click( _

  ByVal sender As Object, _

  ByVal e As EventArgs) Handles setTextBackgroundWorkerBtn.Click

  Me.backgroundWorker1.WorkerSupportsCancellation = True

  Me.backgroundWorker1.RunWorkerAsync()

  End Sub

  Private Sub backgroundWorker1_RunWorkerCompleted( _

  ByVal sender As Object, _

  ByVal e As RunWorkerCompletedEventArgs) _

  Handles backgroundWorker1.RunWorkerCompleted

  Me.textBox1.Text = _

  x.ToString & " This text was set safely by BackgroundWorker."

  End Sub

  <STAThread()> _

  Shared Sub Main()

  Application.EnableVisualStyles()

  Application.Run(New Form1())

  End Sub

  Public x As Long

  Private Sub backgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles backgroundWorker1.DoWork

  For x = 1 To 2450000000

  If backgroundWorker1.CancellationPending Then

  Exit Sub

  End If

  x += 1

  Next

  End Sub

  Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

  Me.backgroundWorker1.CancelAsync()

  End Sub

  End Class

  
  
  
• Ending a sub-routine/thread from an event