Ciao un esempio che mi e' stato utile per capire il funzionamento dei thread e' questo, e' molto semplice da capire:
codice:
Option Explicit On
Option Strict On
Imports System.Threading

' **********************************************************************************************
' * Created In VS2005 *
' * Example of multi or worker threading in VB.Net with start & stop of the worker thread *
' * With invoking to update progress bar & textbox *
' * Create a form with 2x buttons and 1x textbox & 1 x progress bar *
' * Modified from the MicroSoft Help So it actually works!! *
' **********************************************************************************************

Public Class Form1
Dim WorkerThread As Thread 'Create the worker thread
Dim NewVal As Integer 'New Value of progress bar & textbox
Dim StopThread As Boolean = True 'Boolean Value used to halt the endless loop

Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
If StopThread = False Then
StopThread = True
Else
StopThread = False
WorkerThread = New Thread(AddressOf ThreadTask)
WorkerThread.IsBackground = True
WorkerThread.Start()
End If
End Sub

Private Sub ThreadTask()
Dim ProgBarStep As Integer
Dim RandomNo As New Random()
Do Until StopThread = True
ProgBarStep = ProgressBar1.Step * RandomNo.Next(-1, 2)
NewVal = ProgressBar1.Value + ProgBarStep
If NewVal > ProgressBar1.Maximum Then
NewVal = ProgressBar1.Maximum
ElseIf NewVal < ProgressBar1.Minimum Then
NewVal = ProgressBar1.Minimum
End If
Me.ProgressBar1.Invoke(New MethodInvoker(AddressOf InvokeProgBar1))
Me.ProgressBar1.Invoke(New MethodInvoker(AddressOf InvokeTextBox1))
Thread.Sleep(100)
Loop
End Sub

Private Sub InvokeProgBar1()
Me.ProgressBar1.Value = CInt(NewVal)
End Sub

Private Sub InvokeTextBox1()
Me.TextBox1.Text = CStr(NewVal)
End Sub

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
MessageBox.Show("This is the main thread")
End Sub
End Class