There is a private variable in my WebForm, it was assigned with value during Page.Load function. But when I try to get the value in button click event, it becomes null value, any advise would be appreciated, thanks.

Here is my piece of code :

Private myReference As String

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    AddNewRecord()
End Sub

Private Sub AddNewRecord()
    Me.myReference = "ABC00001"
End Sub

Protected Sub btnAdd_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnAdd.Click
    ' Show null value ?
    Msgbox(Me.myReference)
End Sub