Creating a new thread

[Emcrank]

A thread is a fork of operation within the application
To create a new one put this at top of code under Class but not in a sub

Private running As Boolean = True
Private t As Threading.Thread

Then put these in the correct places

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
t = New Threading.Thread(New Threading.ThreadStart(AddressOf threadfunc))
t.IsBackground = True
t.Start()
End Sub
 
Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
running = False
If t.IsAlive AndAlso (Not t.Join(1000)) Then
     t.Abort()
End If
End Sub
 
Private Sub threadfunc()
While running
      'PUT YOUR CODE HERE
End While
End Sub

[sk8er_boi]

very nice & easy... thx for the tip

i have 1 question though ....
how do i re-run the thread ?
for eg. i have inserted execution of a batch file under the thread using :

Private Sub threadfunc()
        While running
            Shell("c:\mymusic\list.bat", AppWinStyle.Hide, True)
            running = False
        End While
    End Sub

batch file takes abt few seconds to run & then i dump batch file's output into a text box on my form, it works fine for the first time but then when i try to run it for the second time it says :

"Thread is running or terminated; it cannot restart."


here's my full code if it helps, it simply lists the contents of directory & dumps it in a textbox, i know i can do this w/o a batch file, but i just wanted to test the "threading" stuff, & i knw it's a crappy one coz i'm just a beginner in vb .net ;-)

Imports System.IO

Public Class Form1
    Dim t = New Threading.Thread(New Threading.ThreadStart(AddressOf threadfunc))
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim fiFile As New System.IO.FileInfo("c:\mymusic\list.bat")
        fiFile.Delete()

        Dim objStreamWriter As StreamWriter

        objStreamWriter = New StreamWriter("c:\mymusic\list.bat", True)

        objStreamWriter.WriteLine("c:")
        objStreamWriter.WriteLine("cd\")
        'objStreamWriter.WriteLine("cd windows")
        objStreamWriter.WriteLine("dir /s > c:\mymusic\list.txt")
        objStreamWriter.Close()
        t.start()
        PictureBox1.Visible = True
        Me.Refresh()
TWAIT:
        If running = False Then
            Dim myOutput = New StreamReader("c:\mymusic\list.txt")
            Dim sValues = myOutput.ReadToEnd
            Me.rtb1.Text = sValues
        Else
            PictureBox1.Visible = True
            Me.Refresh()
            GoTo TWAIT
        End If
        PictureBox1.Visible = False
        running = False
    End Sub
    Private running As Boolean = True

    
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        PictureBox1.Visible = False
    End Sub
    Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
        running = False
        t.Abort()
    End Sub
    Private Sub threadfunc()
        While running
            Shell("c:\mymusic\list.bat", AppWinStyle.Hide, True)
            running = False
        End While
    End Sub
End Class

picturebox? = i have inserted a animated gif that is displayed till the batch file is running in back ground

[chris128]

To re-run the thread, you need to create a new thread and start that. So instead of only creating a new instance of the thread object at class level, create a new instance in your button click event handler. Also, I would suggest that if you want the thread to end when your application ends, you dont need to call Thread.Abort in the form closing event, you can just set the thread's IsBackground property to True and it will automatically close when the application ends (unless of course this is not your main form and you just want the thread to end when this form is closed).

So here is an example of the relevant parts of your code but adapted with both of the above suggestions:

Public Class Form1
    Dim t As Threading.Thread
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim fiFile As New System.IO.FileInfo("c:\mymusic\list.bat")
        fiFile.Delete()

        Dim objStreamWriter As StreamWriter

        objStreamWriter = New StreamWriter("c:\mymusic\list.bat", True)

        objStreamWriter.WriteLine("c:")
        objStreamWriter.WriteLine("cd\")
        'objStreamWriter.WriteLine("cd windows")
        objStreamWriter.WriteLine("dir /s > c:\mymusic\list.txt")
        objStreamWriter.Close()
        t = New Threading.Thread(New Threading.ThreadStart(AddressOf threadfunc))
        t.IsBackground = True
        t.start()

[sk8er_boi]

for some reason, doesn't work the problem occurs when i run it for the second time , it simply does not execute the batch file [under "shell"]

can i do this using background worker ?

[sk8er_boi]

for some reason, doesn't work the problem occurs when i run it for the second time , it simply does not execute the batch file [under "shell"]

can i do this using background worker ?

hey ...GOT IT !

it wasn't the thread, it was problem with my code, i didn't close the StreamReader due to which batch file cudn't write the output , works fine now

thx all for help !

[minitech]

You don't have to abort the thread, which is not good if you can avoid it.
Just call t.Join() after setting the flag to False. Or possibly:

If Not t.Join(1000) Then t.Abort()

. Or you can abort it without setting the flag.

[Emcrank]

Is that better? I changed it in the code above.

If t.IsAlive = True Then
     t.Abort()
End If

[minitech]

Again, you're testing a Boolean value against true ^^. And that wasn't what I said, either. Just put that code exactly where you have all that thread-aborting code.

[minitech]

To sum up:

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
     t = New Threading.Thread(New Threading.ThreadStart(AddressOf threadfunc))
     t.IsBackground = True
     t.Start()
End Sub

Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
     running = False
     If t.IsAlive AndAlso (Not t.Join(1000)) Then t.Abort()
End Sub

Private Sub threadfunc()
     While running
          'PUT YOUR CODE HERE
     End While
End Sub