VB Thread Timer Update UI - vb.net

Question

I made a small program that allows for individual timer countdowns for each button clicked. (e.g. clicking on button 1 will start a countdown for button 1 whilst updating the text on the button itself to reflect the time remaining.)
My worry now is that I'm not sure how well my program would work in the long run. Here's a snippet of the code.
Private Sub depBtn_Clicked(sender As Button, e As EventArgs)
If sender.BackColor = Color.Green Then
Dim depRow() As Data.DataRow
Dim id As String = sender.Name
depRow = DepartmentDataSet.Departments.Select("ID Like '" & id & "'")
sender.BackColor = Color.Red
Dim timerBtn As New DepartmentTimer(sender, depRow(0)("Duration"), depRow(0)("ID"))
Dim TimerDelegate As New System.Threading.TimerCallback(AddressOf TimerTask)
Dim TimerItem As New System.Threading.Timer(TimerDelegate, timerBtn, 0, 1000)
timerBtn.timerRef = TimerItem
End If
End Sub
Private Delegate Sub TimerTaskDelegate(ByVal obj As Object)
Private Sub TimerTask(ByVal obj As Object)
If Me.InvokeRequired() Then
Me.Invoke(New TimerTaskDelegate(AddressOf TimerTask), obj)
Else
Dim depTimer As DepartmentTimer = DirectCast(obj, DepartmentTimer)
depTimer.countDown()
If depTimer.duration = -1 Then
depTimer.finish()
depTimer.timerRef.Dispose()
End If
End If
End Sub
I have read and also experienced that if I were to update on the UI thread directly from the timer callback the whole program would crash. So I ended up using a delegate in accordance to here http://tech.xster.net/tips/invoke-ui-changes-across-threads-on-vb-net/.
Is this a proper way of doing it or am I doing anything redundant/inefficient?
Also when I dispose of the Timer object. How would I go about cleaning up the DepartmentTimer class instance (timerBtn)? The button can be activated again once the timer runs out so I'm afraid that the instances would build up if I don't take care of them properly.
Thanks in advance for any help.

Answer 1

Since you're not actually doing anything with the Timer except immediately Invoking back to the main UI thread, you might as well just use one System.Windows.Forms.Timer and update them all in the same handler.
Something like:
Public Class Form1
Private timers As New List(Of DepartmentTimer)
Private WithEvents Tmr As New System.Windows.Forms.Timer
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles Me.Load
Tmr.Interval = 1000
Tmr.Start()
End Sub
Private Sub depBtn_Clicked(sender As Button, e As EventArgs)
If sender.BackColor = Color.Green Then
Dim depRow() As Data.DataRow
Dim id As String = sender.Name
depRow = DepartmentDataSet.Departments.Select("ID Like '" & id & "'")
sender.BackColor = Color.Red
timers.Add(New DepartmentTimer(sender, depRow(0)("Duration"), depRow(0)("ID")))
End If
End Sub
Private Sub Tmr_Tick(sender As Object, e As EventArgs) Handles Tmr.Tick
For i As Integer = timers.Count - 1 To 0 Step -1
Dim depTimer As DepartmentTimer = timers(i)
depTimer.countDown()
If depTimer.duration = -1 Then
depTimer.finish()
timers.RemoveAt(i)
End If
Next
End Sub
End Class