update form on asynchronous control event - vb.net

Question

A few weeks ago I wrote a wrapper for the ServiceController control to enhance and streamline the base ServiceController. One of the changes I made was to add a monitoring component using the System.Threading.Timer object. On any change of status, an event is raised to the parent class. The actual monitoring works fine, but when the event is handled in the main form, my program abruptly ends - no exceptions, no warning, it just quits. Here's a skeleton version of the control:
Public Class EnhancedServiceController
Inherits ServiceController
Public Event Stopped(ByVal sender As Object, ByVal e As System.EventArgs)
Public Event Started(ByVal sender As Object, ByVal e As System.EventArgs)
Private _LastStatus As System.ServiceProcess.ServiceControllerStatus
Private serviceCheckTimer as System.Threading.Timer
Private serviceCheckTimerDelegate as System.Threading.TimerCallback
...
Private Sub StartMonitor()
MyBase.Refresh()
_LastStatus = MyBase.Status
serviceCheckTimerDelegate = New System.Threading.TimerCallback(AddressOf CheckStatus)
serviceCheckTimer = New System.Threading.Timer(serviceCheckTimerDelegate, Nothing, 0, 60*1000)
End Sub
Private Sub CheckStatus()
MyBase.Refresh()
Dim s As Integer = MyBase.Status
Select Case s
Case ServiceControllerStatus.Stopped
If Not s = _LastStatus Then
RaiseEvent Stopped(Me, New System.EventArgs)
End If
Case ServiceControllerStatus.Running
If Not s = _LastStatus Then
RaiseEvent Started(Me, New System.EventArgs)
End If
End Select
_LastStatus = s
End Sub
End Class
And the form:
Public Class Form1
Private Sub ServiceStarted(ByVal sender As Object, ByVal e As System.EventArgs) Handles ESC.Started
Me.TextBox1.Text = "STARTED"
End Sub
Private Sub ServiceStopped(ByVal sender As Object, ByVal e As System.EventArgs) Handles ESC.Stopped
Me.TextBox1.Text = "STOPPED"
End Sub
End Class
If I had to guess, I'd say that there's some sort of thread problem, but I'm not sure how to handle that in the form. Any ideas?

Answer 1

IF it is a threading issue then you are probably trying to update the UI from a non-UI thread.
So something like this should solve that...
Private Delegate Sub UpdateTextBoxDelegate(byval tText as String)
Private Sub UpdateTextBox(byval tText As String)
If Me.InvokeRequired Then
Me.Invoke(New UpdateTextBoxDelegate(AddressOf UpdateTextBox), tText)
Exit Sub
End If
TextBox1.Text = tText
End Sub
Private Sub ServiceStarted(ByVal sender As Object, ByVal e As System.EventArgs) Handles ESC.Started
UpdateTextBox ("STARTED")
End Sub
Private Sub ServiceStopped(ByVal sender As Object, ByVal e As System.EventArgs) Handles ESC.Stopped
UpdateTextBox("STOPPED")
End Sub