Question

I have a custom class written, which I instantiate from an event procedure similar to

Private Sub EventHandler
    For intForCounter = 1 to intUserEntry
        Dim newObj As New MyClass
        newObj.Property
        newObj.Method()
    Next
End Sub

The class itself looks something like this

Public Property Time As Date
'First attempt:
Dim tmeExec As New Timer
Public Sub Method()
    'Second Attempt
    Dim tmeExec As New Timer
    'A bunch of code for converting a timespan to milliseconds and storing that in intInterval
    With tmeExec
        .Enabled = True
        .Interval = intInterval
    End With
    AddHandler tmeExec.Tick, AddressOf TickHandler
End Sub

Private Sub TickHandler(ByVal myObj As Object, ByVal myArgs As EventArgs)
    Dim tmeSender As Timer = CType(myObj, Timer)
    tmeSender.Stop()
    'Some code here to do something
End Sub

When I had the time placement in the location ‘First Attempt’, everything fired at the last interval specified.

My expectation is that each time a new object is instantiated, a new timer would have been instantiated with it, and so putting the instantiation in the class would be the right way to go. That’s not the case.

But I want to know why it behaves as it does. It’s fine to know HOW something works, but if you know WHY something works, you don’t make that goof again. I asked my professor, but didn’t really understand his answer as fully as I’d like to.

Answer 1

If you place the instantiation of the Timer outside the Method (at ‘First attempt’), then you only have a single timer. Each time you call Method(), you are just setting the properties of the existing timer and adding a new event handler to the existing timer.

By moving the Timer instantiation into the Method(), then each time Method() is called, a new Timer object is created.