Iteration Not Working As Intended - vb.net

Question

I'm using a DO interation to loop a function I'm using to test for internet connectivity. The code is working fine, except that when one of the tests is satisfied the loop stops. I want this to continue in the background while the program is running. How can I get this to work?
Private Sub checkInternet()
Dim InetChecker As Boolean
InetChecker = CheckForInternetConnection()
Do While LabelCount.Text <> ""
Thread.Sleep(10)
If InetChecker = True Then
Dim image = My.Resources.greenbar
PictureBox4.Image = image
Else
Thread.Sleep(10)
Dim image = My.Resources.redbar
PictureBox4.Image = image
'NoInetConnError.Show()
End If
Loop
End Sub
Your assistance would be greatly appreciated, thanks.

Answer 1

Put a BackgroundWorker on your form (you will find it in the Components section of the Toolbox).
In the Properties window set WorkerReportsProgress to True for your BackgroundWorker.
Insert the following code to your form
Private connected As Boolean
Private Sub BackgroundWorker1_DoWork(ByVal sender As Object, ByVal e As DoWorkEventArgs) _
Handles BackgroundWorker1.DoWork
While True
Dim online = CheckForInternetConnection()
If online <> connected Then
connected = online
BackgroundWorker1.ReportProgress(CInt(online))
End If
Thread.Sleep(500)
End While
End Sub
Private Sub BackgroundWorker1_ProgressChanged(ByVal sender As Object, ByVal e As ProgressChangedEventArgs) _
Handles BackgroundWorker1.ProgressChanged
Dim online As Boolean = CBool(e.ProgressPercentage)
If online Then
PictureBox4.Image = My.Resources.greenbar
Else
PictureBox4.Image = My.Resources.redbar
End If
End Sub
Private Sub Form_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) _
Handles MyBase.Load
' Start the background worker
BackgroundWorker1.RunWorkerAsync()
End Sub
Note that Sub BackgroundWorker1_DoWork runs on a separate thread and does not freeze your form while it is running.

Answer 2

It would be best to do something like this in a Timer and not in a loop.
Private Sub Timer1_Tick(ByVal sender As Object, ByVal e As EventArgs) Handles Timer1.Tick
If CheckForInternetConnection Then
PictureBox4.Image = My.Resources.greenbar
Else
PictureBox4.Image = My.Resources.redbar
End If
End Sub

Answer 3

If you have access to .Net framework 3+ then you could use the DispatcherTimer class which essentially creates an interval (set at whatever length you require) which you can handle the tick event for. When the tick event is raised, you can do your internet connection check.
Modifying the MSDN example for your situation, you could do something like this:
' DispatcherTimer setup
dispatcherTimer = New Threading.DispatcherTimer()
AddHandler dispatcherTimer.Tick, AddressOf dispatcherTimer_Tick
dispatcherTimer.Interval = New TimeSpan(0,0,1) ' Or however long you want
dispatcherTimer.Start()
Private Sub dispatcherTimer_Tick(ByVal sender As Object, ByVal e As EventArgs)
' Checks to see whether an internet connection is still available etc
checkInternet()
' Forcing the CommandManager to raise the RequerySuggested event
CommandManager.InvalidateRequerySuggested()
End Sub