为什么在处理ASP.NET Timer Tick事件时索引变量不增加？

Question

This is a bit of an interesting question. I have an ASP.NET Timer ( Timer1 ) that is supposed to increment an integer variable that I am using to keep track of which item in a menu is selected. Have a look at the Tick event handler.

'Menu_RightSide.Items(TimerMenuIndex).Selected = True`

Protected Sub Timer1_Tick(sender As Object, e As System.EventArgs) Handles Timer1.Tick

    Select Case TimerMenuIndex
            Case 0
                bindDataToChart_locationChrono() 
                TimerMenuIndex += 1
            Case 1
                BindCurrentProgressDataToChart() 
                TimerMenuIndex += 1
            Case 2
                bindDBDataToChart()                   
                TimerMenuIndex += 1
            Case Else
                'Do Something else         
    End Select
End Sub

This seems like it should be relatively simple logic. All I want is for the TimerMenuIndex variable to increment by one when the Tick event handler function is called. However, for some reason, it will not increment.I should mention that TimerMenuIndex is a global variable. I know that the Timer control is AJAX-based, so it shouldn't be calling the Page_Load function when the Timer refreshes the page. I can't think of any reason why this doesn't work. I could be missing something very obvious. Any thoughts?

UPDATE: Here is the Page_Load code that pertains to this functionality:

Protected Sub Page_Load(sender As Object, e As System.EventArgs) Handles Me.Load
     Menu_RightSide.Items(TimerMenuIndex).Selected = True
End Sub

Answer 1

What is happening is the variable gets reset to 0 after the tick event.

You need to declare Shared, this will make the variable retain its value, and

Shared TimerMenuIndex As Integer = 0

I created a sample application for you to try