MultiThreading, Using controls accross threads.

class frmmain
Private Sub cmdTest_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdTest.Click
        cmdTest.Enabled = False
        If bworker.IsBusy = False Then
            bworker.RunWorkerAsync()
        End If
    End Sub

    Private Sub bworker_DoWork(ByVal sender As Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles bworker.DoWork
        Dim xxxx As String
        For x = 0 To 9999999999
'only for wasting time!!
            xxxx = "yo"
            xxxx = "yeah"
        Next
    End Sub

    Private Sub bworker_RunWorkerCompleted(ByVal sender As Object, ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles bworker.RunWorkerCompleted
        cmdTest.Enabled = True

    End Sub
end class

Dim instance As Control
Dim value As Boolean

value = instance.InvokeRequired

Dim instance As Control
Dim method As [Delegate]
Dim returnValue As Object

returnValue = instance.Invoke(method)

Dim instance As Control
Dim value As Boolean

value = instance.IsHandleCreated

' The following example demonstrates the 'Invoke(Delegate)' method of 'Control class.
' A 'ListBox' and a 'Button' control are added to a form, containing a delegate
' which encapsulates a method that adds items to the listbox.This function is executed
' on the thread that owns the underlying handle of the form. When user clicks on button
' the above delegate is executed using 'Invoke' method.

Imports System
Imports System.Drawing
Imports System.Windows.Forms
Imports System.Threading

Public Class MyFormControl
  Inherits Form

  Delegate Sub AddListItem()
  Public myDelegate As AddListItem
  Private myButton As Button
  Private myThread As Thread
  Private myListBox As ListBox

  Public Sub New()
      myButton = New Button()
      myListBox = New ListBox()
      myButton.Location = New Point(72, 160)
      myButton.Size = New Size(152, 32)
      myButton.TabIndex = 1
      myButton.Text = "Add items in list box"
      AddHandler myButton.Click, AddressOf Button_Click
      myListBox.Location = New Point(48, 32)
      myListBox.Name = "myListBox"
      myListBox.Size = New Size(200, 95)
      myListBox.TabIndex = 2
      ClientSize = New Size(292, 273)
      Controls.AddRange(New Control() {myListBox, myButton})
      Text = " 'Control_Invoke' example"
      myDelegate = New AddListItem(AddressOf AddListItemMethod)
  End Sub 'New

  Shared Sub Main()
      Dim myForm As New MyFormControl()
      myForm.ShowDialog()
  End Sub 'Main

  Public Sub AddListItemMethod()
      Dim myItem As String
      Dim i As Integer
      For i = 1 To 5
        myItem = "MyListItem" + i.ToString()
        myListBox.Items.Add(myItem)
        myListBox.Update()
        Thread.Sleep(300)
      Next i
  End Sub 'AddListItemMethod

  Private Sub Button_Click(sender As Object, e As EventArgs)
      myThread = New Thread(New ThreadStart(AddressOf ThreadFunction))
      myThread.Start()
  End Sub 'Button_Click

  Private Sub ThreadFunction()
      Dim myThreadClassObject As New MyThreadClass(Me)
      myThreadClassObject.Run()
  End Sub 'ThreadFunction
End Class 'MyFormControl


' The following code assumes a 'ListBox' and a 'Button' control are added to a form,
' containing a delegate which encapsulates a method that adds items to the listbox.
Public Class MyThreadClass
  Private myFormControl1 As MyFormControl

  Public Sub New(myForm As MyFormControl)
      myFormControl1 = myForm
  End Sub 'New

  Public Sub Run()
      ' Execute the specified delegate on the thread that owns
      ' 'myFormControl1' control's underlying window handle.
      myFormControl1.Invoke(myFormControl1.myDelegate)
  End Sub 'Run

End Class 'MyThreadClass