How can I cancel a thread? - vb.net

Question

I do something in a thread. But sometimes I don't want to wait till all pings are finished.
How can I cancel a thread?
Can you show me please the code?
Private Sub Start_Button_Click(sender As Object, e As EventArgs) Handles Start_Button.Click
DoSomething()
End Sub
Private Sub Cancel_Button_Click(sender As Object, e As EventArgs) Handles Cancel_Button.Click
THRD.Cancel '<-- Thread cancel!??!???
End Sub
Sub DoSomething()
Dim THRD As New Thread(Sub()
Dim IPArea As String = "192.168.1."
Dim LastIP As Integer
For LastIP = 0 To 255
Dim TestIP As String = IPArea & CStr(LastIP)
If My.Computer.Network.Ping(TestIP, 10) Then
ListBox1.Items.Add(TestIP)
End If
Next
End Sub)
THRD.IsBackground = True
THRD.Start()
End Sub

Answer 1

Here is my working solution and this solution is only to show how to move the THRD as a form level variable to allow stopping it when clicking the cancel button. I added some validations to prevent exceptions.
Public Class Form1
Private THRD As Threading.Thread
Private Sub Start_Button_Click(sender As Object, e As EventArgs) Handles Start_Button.Click
DoSomething()
End Sub
Private Sub Cancel_Button_Click(sender As Object, e As EventArgs) Handles Cancel_Button.Click
If THRD IsNot Nothing AndAlso THRD.IsAlive Then
THRD.Abort() '<-- Thread cancel!??!???
THRD = Nothing
AddToList("Stopped.")
Else
AddToList("Thread not running.")
End If
End Sub
Sub DoSomething()
If THRD IsNot Nothing AndAlso THRD.IsAlive Then
AddToList("Still working...")
Exit Sub
End If
THRD = New Threading.Thread(Sub()
Dim IPArea As String = "192.168.1."
Dim LastIP As Integer
For LastIP = 0 To 255
Dim TestIP As String = IPArea & CStr(LastIP)
If My.Computer.Network.Ping(TestIP, 10) Then
AddToList(TestIP)
End If
Next
AddToList("Done")
End Sub)
THRD.IsBackground = True
THRD.Start()
End Sub
''' <summary>
''' Thead-safe add value to list.
''' </summary>
''' <param name="value">The value.</param>
Private Sub AddToList(value As String)
If ListBox1.InvokeRequired Then
ListBox1.Invoke(Sub() ListBox1.Items.Add(value))
Else
ListBox1.Items.Add(value)
End If
End Sub
End Class