Global Variable won't increment/decrement

[Harsh Gupta]

Because everytime your page refreshes, the value of G_Index is set to 1 in your page_load event.

You would need to wrap it in the check condition whether page is postbacking or loading for the first time.

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
 
If Not Page.IsPostBack
     G_Index = 1
End If
 
End Sub